What happens when I take vitamin C tablets every day?

October 31, 2025 •

4 min read

According to the National Institutes of Health, most people in the United States already get enough vitamin C from their diet, meaning supplements may not be necessary for everyone. However, some people still choose to take vitamin C tablets every day, a practice that can have both positive and negative consequences for the body.

Quick Summary

Taking daily vitamin C tablets provides antioxidant and immune support but can cause digestive issues or kidney stones at high doses. Most adults can get sufficient vitamin C through a balanced diet of fruits and vegetables, but supplements can be beneficial for those with deficiencies or specific health conditions. The body excretes unneeded vitamin C, but exceeding the tolerable upper limit daily is discouraged due to risks. Consulting a healthcare provider is essential before starting regular supplementation.

Key Points

Daily Intake Needs: The body requires a regular supply of vitamin C because it cannot be stored, but most people get enough from a balanced diet of fruits and vegetables.
Antioxidant and Immune Support: Daily intake of vitamin C offers antioxidant benefits that protect cells from damage and supports the immune system's function.
Risk of Kidney Stones: Consuming high doses, often above the tolerable upper limit daily, increases the risk of kidney stones, particularly in those with a history of the condition.
Gastrointestinal Side Effects: Excessive amounts of vitamin C can cause mild to moderate digestive issues, including diarrhea, nausea, and stomach cramps.
Enhanced Iron Absorption: Vitamin C can significantly improve the body's absorption of non-heme iron from plant-based sources.
Natural vs. Synthetic: While chemically identical, natural vitamin C from food sources often comes with additional synergistic compounds like bioflavonoids, whereas synthetic versions are isolated nutrients.
Crucial for Specific Conditions: Daily supplements are especially beneficial for people with a vitamin C deficiency, certain chronic diseases, or those undergoing specific treatments.
Upper Limit Exists: For adults, exceeding the 2,000 mg tolerable upper intake level is not recommended due to increased risk of side effects.

The role of vitamin C in the body

Vitamin C, or ascorbic acid, is a water-soluble nutrient with numerous vital functions. It's a potent antioxidant that helps protect cells from damage caused by free radicals, unstable molecules linked to chronic diseases. It is also essential for producing collagen, a protein that maintains healthy skin, bones, and blood vessels, and is crucial for wound healing. The body does not produce or store vitamin C, so a consistent daily intake is required. Most people can meet their needs through diet, but supplements offer an alternative.

Potential benefits of taking daily vitamin C tablets

For individuals with a documented deficiency or certain risk factors, consistent supplementation can provide several benefits:

Enhanced immune function: Vitamin C aids in the production and protection of immune cells, bolstering the body's defenses against infections. While it won't prevent the common cold for most people, it may reduce the duration or severity of symptoms.
Improved iron absorption: Vitamin C significantly enhances the absorption of non-heme iron from plant-based foods, helping prevent or treat iron-deficiency anemia.
Collagen synthesis for skin and joints: By promoting collagen production, daily intake supports the maintenance of healthy skin, connective tissues, and joints. Some studies even link higher intake to a lower risk of skin wrinkling.
Protection for vision: Combined with other vitamins and minerals, vitamin C has shown promise in slowing the progression of age-related macular degeneration (AMD). High dietary intake is also associated with a reduced risk of cataracts.
Brain health support: The antioxidant properties of vitamin C may help protect against oxidative stress in the brain, which is implicated in neurodegenerative conditions.

Risks and side effects of daily vitamin C supplementation

While moderate daily supplementation is generally safe, consuming high doses of vitamin C can lead to adverse effects. The tolerable upper intake level (UL) for adults is 2,000 mg per day, and exceeding this amount increases risk.

Gastrointestinal distress: The most common side effects of high-dose vitamin C are digestive issues, including diarrhea, nausea, stomach cramps, and bloating. The unabsorbed excess vitamin C can irritate the gastrointestinal tract.
Increased risk of kidney stones: High doses of vitamin C can be metabolized into oxalate, a compound that can contribute to the formation of calcium oxalate kidney stones, especially in individuals with a history of them.
Iron overload: For those with hemochromatosis or other conditions that cause excess iron storage, the increased iron absorption facilitated by high vitamin C intake can be harmful.
Medication interactions: High-dose vitamin C can interfere with certain medications, including chemotherapy, estrogen-based therapies, statins, and blood-thinning medication warfarin. It is crucial to consult a healthcare provider if taking these medications.
Nutrient imbalance: Excessive vitamin C intake can potentially affect the absorption and processing of other nutrients, such as vitamin B-12 and copper.

Natural vs. Synthetic Vitamin C

When considering supplementation, it's worth understanding the difference between natural and synthetic forms. Most supplements contain synthetic ascorbic acid, while natural vitamin C is found in whole foods like fruits and vegetables.


Aspect	Synthetic Vitamin C (Ascorbic Acid)	Natural Vitamin C (from Whole Foods)
Source	Produced in a laboratory.	Found naturally in fruits and vegetables.
Chemical Identity	Chemically identical to the vitamin C molecule found in nature.	Chemically identical to synthetic ascorbic acid.
Bioavailability	Bioavailability is slightly superior to or equivalent to vitamin C from food.	Contains additional compounds like bioflavonoids and phytonutrients that can aid absorption and act synergistically.
Completeness	An isolated nutrient, lacking the complex array of other beneficial compounds found in food.	Part of a larger nutritional profile that includes synergistic compounds.
Cost	Generally cheaper to produce and buy.	Typically more expensive as a supplement derived from food sources.

Conclusion: Finding the right balance

Taking vitamin C tablets every day can be a reliable way to meet your daily needs and support overall health, especially if your dietary intake is inconsistent. However, the human body is designed to absorb most nutrients from food, which offers the added benefit of other vitamins, minerals, and compounds that work together synergistically. For most healthy individuals, a balanced diet rich in fruits and vegetables is sufficient and preferable.

For those who choose to supplement, it's essential to stay within recommended guidelines and, critically, below the tolerable upper limit to avoid potential side effects like digestive upset or kidney stones. Before beginning any daily supplement regimen, especially for long-term use or high doses, consult with a healthcare provider to ensure it's appropriate for your health needs and won't interfere with existing conditions or medications.

Sources

Vitamin C - Mayo Clinic - August 14 2025
Vitamin C: Benefits, Side Effects, Dosage, Interactions - Verywell Health - September 08 2025
Too much vitamin C: What are the side effects and risks? - Medical News Today - September 04 2019
Natural Vs Synthetic Vitamins, What's The Difference? – One Organic - January 12 2022
High-dose vitamin C linked to kidney stones in men - Harvard Health - February 05 2013

Frequently Asked Questions

Taking vitamin C daily within recommended guidelines is generally safe for most adults and is below the tolerable upper intake level. However, individuals with a history of kidney stones should consult a doctor, as higher doses may increase their risk of forming new stones.

Yes, high daily doses of vitamin C, particularly exceeding the tolerable upper limit, can increase the risk of developing calcium oxalate kidney stones, as the body metabolizes excess vitamin C into oxalate.

The most common side effects from high daily doses of vitamin C are gastrointestinal issues such as diarrhea, nausea, stomach cramps, and bloating. Headaches and heartburn can also occur.

The recommended dietary allowance (RDA) for adult men is 90 mg and for adult women is 75 mg. For smokers, an additional 35 mg is recommended. Most people meet this requirement through diet alone.

Natural vitamin C from whole foods provides additional beneficial compounds like bioflavonoids. While the ascorbic acid molecule is chemically identical in both, obtaining vitamins from a varied diet is generally preferred for overall health.

For the general population, regular vitamin C supplements do not prevent the common cold. However, they may slightly shorten the duration or reduce the severity of cold symptoms.

People with a history of kidney stones, chronic kidney disease, hemochromatosis (iron overload), or a G6PD deficiency should be cautious with daily vitamin C tablets. Those undergoing cancer treatment or taking specific medications should also consult a doctor.

No, the body does not store vitamin C. It's a water-soluble vitamin, so any excess that is not absorbed is excreted in the urine, which is why a consistent daily intake is important.