C Side Effects: What To Expect

Takeaways

Vitamin C can cause digestive issues in high doses

Headaches may occur from vitamin C supplementation

Skin reactions are possible from topical vitamin C use

Vitamin C interacts with certain medications

Proper dosage and timing can minimize side effects

Some populations have higher risks of vitamin C side effects

Vitamin C: A Double-Edged Sword

Vitamin C is a powerful nutrient that supports the immune system, skin health, and overall well-being. However, like many nutrients, it can have potential side effects. Knowing these possible drawbacks helps us use vitamin C in a safe and effective way.

Understanding the potential negative effects of vitamin C is important for making informed choices. By learning about possible issues, you can maximize the benefits while minimizing the risks. This article will explore some of the less-discussed effects of vitamin C on the body.

This article will discuss some of the hidden impacts of vitamin C and provide information on how to use it safely. Whether you are interested in health or simply curious, this information can be beneficial for you.

Common Side Effects

Digestive Discomfort

Vitamin C can sometimes cause stomach upset, especially in high doses.[1] These issues, often gastrointestinal, are caused by the acidity of vitamin C and its effect on the digestive system.

This happens because the body can only absorb a certain amount of vitamin C at one time. Any excess travels through the digestive system, which can cause irritation in the stomach and intestines.

Common digestive side effects include:

Nausea
Stomach cramps
Diarrhea
Bloating

These symptoms are more likely with doses higher than 2,000 mg daily.[2] Reducing your vitamin C intake usually makes these problems go away quickly.

Headaches and Migraines

Some people report experiencing headaches after taking vitamin C.[3] This side effect isn’t always easy to explain. It may be related to how vitamin C affects body chemistry.

Vitamin C can alter blood sugar levels and also affect the production of neurotransmitters.[4] These changes could lead to headaches in some people. Those who are prone to migraines might be more likely to experience this.

To help manage headaches caused by vitamin C:

Start with a low dose
Increase intake gradually
Take vitamin C with food
Stay hydrated

If you continue to have headaches, it’s a good idea to see a doctor. They can help figure out if vitamin C is the cause.

Skin Reactions

Vitamin C products applied to the skin can sometimes cause problems.[5] Although many use these for anti-aging benefits, there are potential risks. Reactions can range from mild irritation to severe allergic responses.

Different types of skin reactions can include:

Redness
Itching
Dryness
Peeling
Hives (in rare cases)

Factors that may increase the risk of skin reactions are:

Sensitive skin
Allergies to vitamin C or product ingredients
Using high concentrations of vitamin C
Combining with other active skincare ingredients

To reduce the chances of skin problems, begin with a product that has a low concentration of vitamin C. Use it every other day, then gradually use it more often. If irritation happens, stop using it and talk to a dermatologist.

Dosage-Related Side Effects

Recommended Daily Intake

Taking the correct amount of vitamin C is important for preventing side effects. The recommended daily amount differs based on factors such as age, sex, and stage of life.[6]

Here is a general guide for daily vitamin C needs:

Age Group	Male	Female	Pregnancy	Lactation
0-6 months	40 mg	40 mg	–	–
7-12 months	50 mg	50 mg	–	–
1-3 years	15 mg	15 mg	–	–
4-8 years	25 mg	25 mg	–	–
9-13 years	45 mg	45 mg	–	–
14-18 years	75 mg	65 mg	80 mg	115 mg
19+ years	90 mg	75 mg	85 mg	120 mg

These are general guidelines, and your individual needs may differ depending on:

Overall health
Smoking status (smokers need more vitamin C)
Stress levels
Diet quality
Certain medical conditions

Always ask your doctor for personalized advice about how much vitamin C you should take.

Consequences of Excessive Intake

Taking too much vitamin C can lead to health problems. While it is rare to have a vitamin C overdose, excessive intake can cause discomfort and other issues.

The body gets rid of extra vitamin C through urine, so severe toxicity is uncommon.[7] However, regularly taking high doses can lead to several issues.

Here’s how taking too much vitamin C can affect your body:

Digestive system absorbs vitamin C
Bloodstream becomes saturated
Kidneys filter out excess
Unabsorbed vitamin C remains in digestive tract
Excess can cause osmotic diarrhea
Long-term high doses may lead to kidney stones

Symptoms of a vitamin C overdose can include:

Severe diarrhea
Nausea and vomiting
Heartburn
Abdominal cramps
Headache
Insomnia

To avoid these issues, it’s best to stick to the recommended doses. If you experience any symptoms, reduce your intake and talk with a doctor.

Interactions with Medications

Blood Thinners

Vitamin C can interact with blood-thinning medications, which can be risky for people who take anticoagulants.[8] Understanding this connection can help prevent problems.

Vitamin C can affect how the body processes certain blood thinners.[9] It can increase the absorption of drugs like warfarin, which can amplify the blood-thinning effect and increase bleeding risks.

This interaction occurs because vitamin C influences the metabolism of medications by affecting liver enzymes. This can change the amount of the drug in the bloodstream.

If you take blood thinners:

Consult your doctor before starting vitamin C supplements
Maintain consistent vitamin C intake
Monitor blood clotting times regularly
Report any unusual bleeding or bruising

Balancing vitamin C intake with blood thinner use should be done under medical supervision. Your doctor can help adjust doses to make sure it’s safe.

Chemotherapy Drugs

Vitamin C’s effect on chemotherapy drugs is not fully understood. Some studies suggest it might make treatment less effective, while others suggest benefits.[10] This complex relationship needs careful consideration.

These interactions can occur because vitamin C acts as an antioxidant and can protect cells from damage. While this is generally a good thing, it might also protect cancer cells during chemotherapy.

Chemotherapy drugs that may interact with vitamin C include:

Doxorubicin
Methotrexate
Cisplatin
Vincristine

Cancer patients should always discuss their vitamin C intake with their oncologist to ensure their treatment is both safe and effective.

Other Medication Interactions

Vitamin C can interact with other medications besides blood thinners and chemo drugs.[11] These interactions can change how well the drug works or increase side effects.

Some common medications and their possible interactions with Vitamin C are:

Medication Type	Potential Interaction
Estrogen-based contraceptives	May increase estrogen levels
Aluminum-containing antacids	Can increase aluminum absorption
Statins	Might decrease drug effectiveness
Niacin	Can reduce flushing side effects
Tetracycline antibiotics	May decrease absorption

Always tell your doctor if you are taking vitamin C supplements. This will help them prevent any unexpected interactions and make sure your medications are safe for you.

Special Populations and Risk Factors

Pregnancy and Breastfeeding

Vitamin C is important during pregnancy and breastfeeding as it helps with fetal development and breast milk production. However, high doses can pose risks.

During pregnancy, the need for vitamin C increases slightly to about 85 mg per day.[12] For breastfeeding, it increases to about 120 mg per day, supporting both the mother and the baby.[13]

Risks of taking too much Vitamin C during pregnancy include:

Increased risk of preterm birth
Newborn scurvy after birth (rare)
Excessive iron absorption

Benefits of having enough Vitamin C during pregnancy and breastfeeding:

Supports immune function
Aids in iron absorption
Promotes healthy skin and tissues

To consume Vitamin C safely:

Stick to recommended doses
Choose prenatal vitamins with appropriate amounts
Discuss supplementation with your obstetrician

Balancing your vitamin C intake is essential for the best outcomes for both the mother and the child.

Kidney Disorders

People with kidney problems need to be extra careful with vitamin C. Kidney issues can affect how the body processes this vitamin, which can raise the risk of side effects.

Healthy kidneys remove excess vitamin C from the blood through urine.[14] When kidneys are not functioning well, this process doesn’t work as effectively and Vitamin C can build up in the body.

Potential risks for people with kidney problems include:

Increased oxalate levels (leading to kidney stones)
Worsening of existing kidney damage
Interference with dialysis treatments

Medical supervision is very important for people with kidney problems who take vitamin C. A kidney specialist can advise you on safe amounts and may recommend limiting both supplements and vitamin C-rich foods.

Genetic Disorders

Some genetic conditions can affect how the body handles vitamin C. These conditions can make people more sensitive to its side effects, so it’s good to know about these risks.

Hemochromatosis, which causes iron overload in the body, is one condition to be aware of. Because vitamin C increases iron absorption, it can worsen iron build up in people with this condition.[15]

Other genetic disorders that may increase sensitivity to vitamin C include:

Glucose-6-phosphate dehydrogenase deficiency
Sickle cell anemia
Thalassemia

If you have any of these conditions, consult a genetic counselor or specialist. They can give you tailored advice on vitamin C consumption.

Vitamin C in Different Forms

Oral Supplements

Vitamin C supplements taken by mouth come in different forms. Each type has different benefits and possible side effects. Understanding these differences helps you make informed choices.

Common forms of oral vitamin C supplements are:

Tablets
Capsules
Powders
Chewables
Liquids

Tablets and capsules are common because they are convenient and provide accurate dosing. Powders allow for easier dose adjustments. Chewables and liquids are good for those who have trouble swallowing pills.

Different forms of Vitamin C have different side effects. Tablets might cause more stomach irritation.[16] Liquids might affect tooth enamel because of acidity.[17] Buffered forms can help reduce stomach discomfort.

Steps to choose the right oral Vitamin C supplement:

Consider your dosage needs
Evaluate your tolerance for different forms
Check for additional ingredients
Read reviews and product information
Consult a healthcare provider for personalized advice

Remember that quality matters. Choose well-known brands and look for certifications from third-party testing.

Topical Applications

Topical vitamin C products are often used in skincare. They are promoted to brighten skin and provide anti-aging benefits. However, they can also cause side effects.

How your skin reacts to topical vitamin C depends on:

Concentration of vitamin C
Product formulation
Individual skin type
Other ingredients in the product

Common forms of topical Vitamin C include:

Serums
Creams
Moisturizers
Face masks

Possible side effects of using topical vitamin C:

Redness
Itching
Dryness
Tingling sensation
Yellowing of the skin (with improper formulations)

Tips for using topical vitamin C products safely:

Start with a low concentration (around 10%)
Do a patch test before full application
Apply at night to avoid sun sensitivity
Use sunscreen during the day
Store products properly to prevent oxidation

Talk to a dermatologist if you have persistent skin irritation. They can help you find products that are suitable for your skin type.

Intravenous (IV) Vitamin C

Intravenous (IV) Vitamin C therapy involves high doses of vitamin C given directly into the bloodstream.[18] This method bypasses the digestive system. It’s used for some medical treatments and alternative therapies.

IV vitamin C can lead to much higher concentrations of vitamin C in the blood than supplements taken by mouth. This leads to different effects and risks.

Potential side effects of IV Vitamin C:

Vein irritation at injection site
Sudden drop in blood sugar
Fluid overload in people with heart or kidney issues
Hemolysis in people with G6PD deficiency

IV vitamin C therapy needs medical supervision. This isn’t a simple treatment. Only trained healthcare providers should administer it.

Reasons for using IV vitamin C:

Cancer supportive care
Treating severe vitamin C deficiency
Burn recovery
Certain infections

Always discuss the risks and benefits with a doctor before using IV vitamin C therapy.

Managing and Preventing Side Effects

Gradual Dosage Increase

Starting with lower doses of vitamin C can help prevent many side effects. The body adjusts more easily to gradual changes. This can help minimize digestive and other related issues.

Why start with a low dose? The body can only absorb a limited amount of vitamin C.[19] Suddenly introducing large amounts can overwhelm this system and lead to waste and side effects.

How to safely increase your vitamin C dosage:

Begin with a low dose (250-500 mg daily)
Monitor for any side effects
Increase by 250 mg every week
Stop increasing if side effects occur
Find your optimal dose based on tolerance

This gradual approach allows your body to adjust and helps you find your personal tolerance level. Remember that taking more vitamins is not always better.

Timing of Intake

When you take Vitamin C is important, as timing can affect absorption and side effects. Optimizing when you take it improves benefits and reduces risks.

Best times to take Vitamin C supplements:

With meals to reduce stomach irritation
In divided doses throughout the day for better absorption
Before bed if it doesn’t affect your sleep

Avoid taking vitamin C:

On an empty stomach if you’re prone to acid reflux
Close to bedtime if it disrupts your sleep
At the same time as iron supplements (space them 2 hours apart)

Tips for timing your Vitamin C intake:

Consistent daily timing improves absorption
Pair with vitamin C-rich foods for natural synergy
Adjust timing if you notice any discomfort
Consider your medication schedule to avoid interactions

Experiment to find what works best for you as everyone responds differently to when they take supplements.

Hydration and Diet

Drinking enough water can help manage vitamin C side effects.[20] Staying well-hydrated helps the body process and remove extra vitamin C. It also helps with general health.

What you eat can affect how your body processes vitamin C. Certain foods can enhance its benefits, while others might increase the risk of side effects.

Foods that may help reduce vitamin C side effects:

Food	Benefit
Bananas	Soothe stomach and provide potassium
Yogurt	Supports digestive health
Whole grains	Stabilize blood sugar
Leafy greens	Provide complementary nutrients
Berries	Offer natural vitamin C and antioxidants

Tips for staying hydrated when taking Vitamin C:

Drink water throughout the day
Increase fluid intake if you experience diarrhea
Choose water over sugary or caffeinated drinks
Monitor urine color (pale yellow indicates good hydration)

A balanced diet helps the body use vitamin C efficiently. It provides cofactors, which are substances that help vitamin C work. Try to include a variety of fruits, vegetables, and whole foods in your diet.

When to Seek Medical Attention

While vitamin C side effects are usually mild, some situations call for medical care. Recognizing these signs will ensure that you get help when you need it.

Symptoms that require medical consultation:

Severe or persistent diarrhea
Signs of an allergic reaction (hives, difficulty breathing)
Unexplained bruising or bleeding
Kidney pain or signs of kidney stones
Persistent headaches or migraines

Although rare, serious complications of Vitamin C include:

Kidney stone formation
Iron overload in susceptible individuals
Severe allergic reactions

Warning signs that indicate a need for immediate medical attention:

Chest pain
Shortness of breath
Sudden severe headache
Swelling of face, lips, or tongue
Severe abdominal pain

Don’t hesitate to contact your doctor if you have any concerns. They can help determine if your symptoms are related to Vitamin C or another issue.

FAQ: People Also Ask

What are the side effects of taking vitamin C daily?

Daily vitamin C intake can cause mild side effects like stomach upset, diarrhea, or headaches.[21] These usually occur with high doses. Most people tolerate regular, moderate doses well.

Can too much vitamin C cause kidney stones?

Yes, excessive vitamin C intake may increase the risk of kidney stones in some people.[22] This happens because vitamin C can increase oxalate production in the body.

How much vitamin C is too much?

The upper limit for adults is 2,000 mg per day.[23] Doses above this increase the risk of side effects. However, some people may experience issues at lower doses.

Does vitamin C interact with any medications?

Yes, vitamin C can interact with several medications. These include blood thinners, chemotherapy drugs, and estrogen-based contraceptives.[24] Always inform your doctor about your vitamin C intake.

Can vitamin C cause acid reflux?

In some people, high doses of vitamin C can cause or worsen acid reflux.[25] Taking vitamin C with food or choosing buffered forms may help reduce this effect.

Is it safe to take vitamin C during pregnancy?

Vitamin C is generally safe during pregnancy when taken at recommended doses. However, excessive amounts may pose risks.[26] Consult your obstetrician for personalized advice.

Can vitamin C supplements cause insomnia?

Some people report difficulty sleeping after taking vitamin C, especially in high doses or late in the day.[27] Taking it earlier may help avoid sleep disruptions.

Does vitamin C affect blood sugar levels?

Vitamin C can influence blood sugar levels. It may lower blood sugar in some cases. People with diabetes should monitor their levels when starting or changing vitamin C intake.[28]

Can vitamin C supplements cause weight gain?

Vitamin C itself doesn’t cause weight gain.[29] However, some vitamin C supplements contain added sugars or calories. Check labels and choose sugar-free options if concerned about weight.

Are there any long-term side effects of taking vitamin C?

Long-term use of high-dose vitamin C may increase the risk of kidney stones.[30] Otherwise, no significant long-term side effects have been established for typical doses.

By discussing these common questions, this article has covered the most important aspects of vitamin C side effects. While vitamin C provides many benefits, it’s important to use it safely. Pay attention to your body and consult a doctor if needed.

Vitamin C is an important nutrient that benefits the immune system, skin health and general well-being. Like any powerful nutrient, it must be used carefully. Understanding the potential side effects will help you benefit from it while minimizing the risks.

This article has explored many aspects of vitamin C side effects. From common digestive issues to rare but serious complications, we’ve discussed the range of potential effects. We’ve also explored how different forms of vitamin C—oral, topical, and intravenous—affect the body in different ways.

Key takeaways include:

Start with low doses and increase gradually
Pay attention to timing and hydration
Be aware of potential interactions with medications
Consider individual factors like pregnancy or kidney health
Recognize when to seek medical attention

Remember that everyone’s body responds differently to supplements. What works well for one person might cause problems for another. This shows the importance of a personalized approach to vitamin C supplementation.

To conclude, informed decision-making is crucial. Knowing about the effects of Vitamin C will allow you to use it effectively and safely. Whether you want to boost your immune system, improve your skin health or improve overall health, knowing about both sides of Vitamin C is important.

Continue to learn about your health. Keep learning about the supplements you take. Work with healthcare providers to make a vitamin routine that is right for you. Using this approach will help you maximize the benefits of vitamin C while minimizing the potential downsides.

Vitamin C is a valuable tool for improving health. When used correctly, it can greatly benefit your well-being. By staying informed and attentive, you can enjoy its benefits and navigate its challenges. We wish you health, balance and well-being.

Fact Check

[1]

Claim: Vitamin C can sometimes cause stomach upset, especially in high doses.

Fact check: True. High doses of vitamin C can cause gastrointestinal issues.

High doses of vitamin C can cause nausea, diarrhea and abdominal cramping due to its acidity and effect on the digestive system.

Source: “SVCT2–mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694147/

[2]

Claim: These symptoms are more likely with doses higher than 2,000 mg daily.

Fact check: True. Gastrointestinal symptoms are more common with vitamin C doses above 2000 mg.

The tolerable upper intake level (UL) for vitamin C is 2,000 mg per day. Consuming more than this may cause adverse effects. However, some people may experience side effects at much lower doses.

[3]

Claim: Some people report experiencing headaches after taking vitamin C.

Fact check: Potentially True. Headaches can be a side effect, although the mechanism is not well understood.

While not a common side effect, some individuals have reported headaches after taking Vitamin C. This may be due to various interactions such as changes in neurotransmitters, but it is not fully understood.

[4]

Claim: Vitamin C can alter blood sugar levels and also affect the production of neurotransmitters.

Fact check: Potentially True. Vitamin C can influence blood sugar levels and neurotransmitter activity.

Vitamin C has demonstrated some impact on glucose metabolism and neurotransmitter synthesis; however, its clinical relevance is not fully understood. More research is needed to determine the scope of its effects.

Source: “Plasma ascorbic acid and the risk of islet autoimmunity and type 1 diabetes: the TEDDY study” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6946743/

[5]

Claim: Vitamin C products applied to the skin can sometimes cause problems.

Fact check: True. Topical vitamin C can cause skin irritation or allergic reactions.

Topical vitamin C can cause skin irritation, redness, itching or a rash. Starting with low concentrations and testing on a small area first can help to mitigate this risk.

Source: “Assessment of the Influence of the Selected Range of Visible Light Radiation on the Durability of the Gel with Ascorbic Acid and Its Derivative” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9369315/

[6]

Claim: The recommended daily amount differs based on factors such as age, sex, and stage of life.

Fact check: True. The recommended daily allowance (RDA) for vitamin C varies.

The recommended daily allowance (RDA) of Vitamin C varies according to age, sex, pregnancy and lactation status. For example, smokers require more Vitamin C than non-smokers.

[7]

Claim: The body gets rid of extra vitamin C through urine, so severe toxicity is uncommon.

Fact check: True. Excess vitamin C is excreted through urine.

Vitamin C is a water-soluble vitamin. Excess amounts that are not used are excreted through the urine, so it is less likely to accumulate to toxic levels.

[8]

Claim: Vitamin C can interact with blood-thinning medications, which can be risky for people who take anticoagulants.

Fact check: True. Vitamin C can interact with blood thinners.

High doses of Vitamin C can increase the absorption of anticoagulant drugs like warfarin and amplify the blood-thinning effect and increase bleeding risk.

[9]

Claim: Vitamin C can affect how the body processes certain blood thinners.

Fact check: True. Vitamin C can alter the metabolism of certain blood thinners.

Vitamin C can alter the metabolism of some blood thinners by affecting liver enzymes, potentially changing drug concentrations in the bloodstream.

[10]

Claim: Some studies suggest it might make treatment less effective, while others suggest benefits.

Fact check: True. The impact of vitamin C on chemotherapy is complex and varies.

Studies investigating the interaction of vitamin C and chemotherapy have yielded conflicting results. The complex interplay between Vitamin C’s anti-oxidant properties and chemotherapy requires careful consideration.

[11]

Claim: Vitamin C can interact with other medications besides blood thinners and chemo drugs.

Fact check: True. Vitamin C can interact with various medications.

Vitamin C can interfere with the effectiveness of certain medications by altering their absorption or metabolism. Always check with your doctor or pharmacist regarding potential drug interactions.

[12]

Claim: During pregnancy, the need for vitamin C increases slightly to about 85 mg per day.

Fact check: True. Pregnant women require a higher intake of vitamin C.

The Recommended Dietary Allowance (RDA) of vitamin C for pregnant women is 85 mg per day, higher than the general adult recommendation of 75 mg per day.

[13]

Claim: For breastfeeding, it increases to about 120 mg per day, supporting both the mother and the baby.

Fact check: True. Breastfeeding women require a higher intake of vitamin C.

The Recommended Dietary Allowance (RDA) of vitamin C for breastfeeding women is 120 mg per day, higher than the general adult recommendation of 75 mg per day.

[14]

Claim: Healthy kidneys remove excess vitamin C from the blood through urine.

Fact check: True. The kidneys play a key role in vitamin C excretion.

The kidneys filter excess vitamin C from the blood and eliminate it through urine. Impaired kidney function can lead to a build-up of vitamin C in the body.

[15]

Claim: Hemochromatosis, which causes iron overload in the body, is one condition to be aware of. Because vitamin C increases iron absorption, it can worsen iron build up in people with this condition.

Fact check: True. Vitamin C can worsen iron overload in people with hemochromatosis.

Vitamin C enhances non-heme iron absorption which can exacerbate iron overload in individuals with hemochromatosis.

Source: “Degradation of Patulin in Pear Juice and Apple Juice by Ascorbic Acid and the Combination of Ascorbic Acid and Ferrous Iron” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9696537/

[16]

Claim: Tablets might cause more stomach irritation.

Fact check: Potentially True. Some forms of vitamin C can cause more gastric irritation.

Tablets, especially non-buffered forms, can sometimes cause more stomach irritation due to their acidity. Buffered forms are often better tolerated.

[17]

Claim: Liquids might affect tooth enamel because of acidity.

Fact check: Potentially True. Liquid forms of vitamin C can affect tooth enamel.

Liquid forms of vitamin C, due to their acidity, may contribute to tooth enamel erosion over time. Rinsing with water after consumption may help reduce this effect.

[18]

Claim: Intravenous (IV) Vitamin C therapy involves high doses of vitamin C given directly into the bloodstream.

Fact check: True. IV vitamin C involves direct administration into the bloodstream.

IV vitamin C therapy bypasses the digestive system and delivers high doses of vitamin C directly into the bloodstream. This method allows for much higher blood concentrations of the vitamin.

[19]

Claim: The body can only absorb a limited amount of vitamin C.

Fact check: True. The body has a limited capacity for vitamin C absorption.

The absorption of vitamin C decreases as the dose increases. The intestinal absorption mechanism becomes saturated. Consuming small doses frequently is more effective at increasing the body’s vitamin C stores.

[20]

Claim: Drinking enough water can help manage vitamin C side effects.

Fact check: True. Hydration can help manage some vitamin C side effects.

Adequate hydration helps to dilute the acidity of vitamin C in the digestive system. It also assists with the excretion of excess vitamin C through the urine.

[21]

Claim: Daily vitamin C intake can cause mild side effects like stomach upset, diarrhea, or headaches.

Fact check: True. Daily vitamin C intake, especially at high doses, can cause digestive issues or headaches.

High doses of daily vitamin C intake may lead to side effects, particularly mild gastrointestinal issues like stomach upset and diarrhea, or headaches. Regular, moderate doses are typically well tolerated.

[22]

Claim: Yes, excessive vitamin C intake may increase the risk of kidney stones in some people.

Fact check: True. High doses of vitamin C may increase kidney stone risk in susceptible individuals.

Excess vitamin C can increase oxalate production in the body, which can then contribute to kidney stone formation in predisposed individuals.

Source: “Vitamins as regulators of calcium-containing kidney stones — new perspectives on the role of the gut microbiome” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10169205/

[23]

Claim: The upper limit for adults is 2,000 mg per day.

Fact check: True. The tolerable upper intake level for vitamin C is 2000 mg.

The Tolerable Upper Intake Level (UL) for vitamin C, which is the maximum daily dose that’s unlikely to cause adverse effects, is 2000 mg for adults. Doses exceeding this can cause a higher risk of side effects.

[24]

Claim: Yes, vitamin C can interact with several medications. These include blood thinners, chemotherapy drugs, and estrogen-based contraceptives.

Fact check: True. Vitamin C can interact with various medications.

Vitamin C may interact with medications such as anticoagulants, certain chemotherapy drugs, and some estrogen-based contraceptives. Individuals taking these medications should consult their doctor regarding vitamin C supplementation.

[25]

Claim: In some people, high doses of vitamin C can cause or worsen acid reflux.

Fact check: Potentially True. High doses of vitamin C may trigger or exacerbate acid reflux.

The acidity of high doses of Vitamin C may lead to acid reflux in some people. Taking Vitamin C with food or using a buffered formulation may help reduce this risk.

[26]

Claim: Vitamin C is generally safe during pregnancy when taken at recommended doses. However, excessive amounts may pose risks.

Fact check: True. Vitamin C is generally safe in pregnancy at recommended doses, but high doses carry risks.

Vitamin C is essential during pregnancy. However excessive doses should be avoided and women should consult their doctor for personalized advice.

[27]

Claim: Some people report difficulty sleeping after taking vitamin C, especially in high doses or late in the day.

Fact check: Potentially True. High doses of vitamin C taken before bed may disrupt sleep.

Anecdotal reports suggest that some people may experience insomnia after taking large doses of vitamin C, particularly late in the day. Taking it earlier in the day may be helpful. Further research is needed to determine its specific effect on sleep.

[28]

Claim: Vitamin C can influence blood sugar levels. It may lower blood sugar in some cases. People with diabetes should monitor their levels when starting or changing vitamin C intake.

Fact check: Potentially True. Vitamin C may affect blood sugar levels.

Vitamin C may influence blood sugar and should be monitored closely by those with diabetes when starting vitamin C supplementation. More research is needed to determine the clinical relevance of these findings.

Source: “Plasma ascorbic acid and the risk of islet autoimmunity and type 1 diabetes: the TEDDY study” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6946743/

[29]

Claim: Vitamin C itself doesn’t cause weight gain.

Fact check: True. Vitamin C does not directly cause weight gain.

Vitamin C is a low calorie micronutrient and does not contribute to weight gain. Some formulations of vitamin C supplements may contain added calories or sugar which may contribute to weight gain if consumed in high amounts.

[30]

Claim: Long-term use of high-dose vitamin C may increase the risk of kidney stones.

Fact check: True. Long-term use of high-dose vitamin C can increase kidney stone risk.

Chronic intake of high doses of vitamin C can increase the risk of kidney stones in susceptible individuals, due to increased oxalate production.