The Extreme Risks of Trying to Get 100g of Vitamin C

January 2, 2026 •

4 min read

The Tolerable Upper Intake Level for vitamin C in adults is 2,000 milligrams (2g) per day, making the prospect of trying to get 100g of vitamin C not only unnecessary but extremely dangerous. This is a pharmacological dosage level, not a nutritional one, and attempting it without strict medical supervision can lead to severe health consequences, including organ damage.

Quick Summary

This article explains why attempting to consume 100 grams of vitamin C is highly unsafe. It details the body's absorption limitations, outlines the significant health risks involved, and contrasts this extreme dosage with recommended daily intakes.

Key Points

100g is Extremely Dangerous: A 100,000 mg dose is 50 times the Tolerable Upper Intake Level (UL) of 2,000 mg and is highly unsafe for oral consumption.
Oral Absorption is Limited: The body absorbs less than 50% of vitamin C at doses above 1,000 mg, leading to unabsorbed excess that causes digestive issues.
High Risk of Kidney Stones: Megadosing significantly increases the production of oxalate, which can lead to the formation of painful kidney stones and, in rare cases, irreversible kidney damage.
Clinical vs. Self-Administration: Extremely high doses (e.g., via IV) are only used in supervised medical settings for specific treatments and should never be attempted at home.
Best to Stick to a Balanced Diet: For optimal health, meet your daily requirement of 75-90 mg by eating a variety of fruits and vegetables, rather than relying on risky megadoses.

Understanding the Recommended Daily Allowance vs. Megadosing

Before considering an astronomical amount like 100 grams (100,000 mg) of vitamin C, it is crucial to understand the normal daily requirements. For adult men, the Recommended Dietary Allowance (RDA) is 90 mg per day, while adult women need 75 mg. Most people can easily meet this requirement through a balanced diet rich in fruits and vegetables. Beyond the RDA, health authorities have established a Tolerable Upper Intake Level (UL) to define the maximum daily intake unlikely to cause adverse health effects. For adults, this limit is set at 2,000 mg (2g) per day. A 100g dose is 50 times higher than this established safety limit.

The Body's Limited Absorption Capacity

Consuming vitamin C orally is limited by the body's absorption capacity, which is a key reason why megadosing is ineffective and risky. Intestinal absorption of vitamin C is saturable and dose-dependent. At typical dietary intakes (30–180 mg), absorption is high, around 70-90%. However, at a dose of 1,000 mg (1g), absorption drops to less than 50%, with the unabsorbed portion causing digestive distress. Attempting to ingest 100g of vitamin C would result in a massive amount of unabsorbed ascorbic acid passing through the digestive system, leading to severe gastrointestinal side effects and potentially dangerous metabolic shifts.

Significant Dangers of Exceeding the Upper Limit

Crossing the 2,000 mg UL barrier significantly elevates the risk of serious health complications. The most commonly reported side effects at high doses include:

Diarrhea
Nausea and vomiting
Stomach cramps and bloating
Headache
Heartburn

Far more concerning are the severe, organ-threatening risks associated with toxic megadoses, particularly for individuals with pre-existing conditions.

Kidney Stones: Excess vitamin C is metabolized into oxalate, which is excreted in the urine. High urinary oxalate can precipitate with calcium to form painful kidney stones. Individuals with a history of kidney stones are at a much higher risk. In one tragic case, a patient receiving 600 grams of intravenous vitamin C for alternative cancer therapy developed acute kidney injury requiring lifelong hemodialysis due to calcium oxalate crystal deposition.
Iron Overload: Vitamin C increases the absorption of nonheme iron from plant-based foods. In individuals with hemochromatosis, a disorder causing excessive iron accumulation, high vitamin C intake can worsen iron overload and cause severe tissue damage.
Drug Interactions: High doses of vitamin C can interfere with medications, including chemotherapy drugs, statins, and blood thinners like warfarin.
Other Risks: In rare cases, high intravenous doses have caused red blood cell breakdown in individuals with a specific metabolic disorder called G6PD deficiency.

High-Dose Vitamin C in Medical Contexts

It is important to differentiate between reckless, self-administered megadosing and controlled, medically supervised high-dose therapy. In specific clinical settings, such as to improve the quality of life in advanced cancer patients, intravenous (IV) vitamin C is administered under strict medical protocols. An IV drip bypasses the intestinal absorption bottleneck, allowing extremely high concentrations of vitamin C to reach the bloodstream. These levels are selectively cytotoxic to tumor cells in vitro, but the therapy is experimental and requires careful patient screening and monitoring due to the aforementioned risks. This is not a treatment that can or should ever be attempted by an individual at home.

Achieving a Healthy, Non-Toxic Vitamin C Intake

Instead of chasing a dangerous megadose, focus on a balanced dietary intake. Raw fruits and vegetables are the best sources, as prolonged cooking and storage can reduce vitamin C content.

Excellent Dietary Sources of Vitamin C (per 100g)

Guava: ~100 mg
Blackcurrants: ~200 mg
Red bell peppers (raw): ~126 mg
Broccoli: ~90 mg
Kiwi: ~90 mg
Strawberries: ~57 mg
Orange: ~52 mg

Comparison of Vitamin C Dosages


Dosage Level	Amount (per day)	Primary Source	Body Absorption	Safety Profile	Potential Health Outcomes
Recommended Dietary Allowance (RDA)	75-90 mg	Balanced diet of fruits and vegetables	70-90%	Very Safe	Healthy immune function, collagen synthesis, iron absorption, prevents deficiency
Tolerable Upper Intake Level (UL)	2,000 mg	Food + Supplementation	< 50%	Moderately Safe	General antioxidant benefits, possible reduction in cold duration
Megadose (100g)	100,000 mg	Multiple supplements, medical IV	Very Low via Oral Route	Extremely Dangerous	Severe diarrhea, nausea, high risk of kidney stones, potential organ damage

Conclusion

While vitamin C is a vital nutrient, the notion of consuming 100g is a deeply misguided and dangerous idea. The human body is simply not equipped to process such a massive oral dose, and doing so risks severe and potentially irreversible health complications, including kidney damage. The concept of 'megadosing' only exists in tightly controlled medical contexts, such as intravenous therapy for specific conditions, and is a world away from dietary recommendations. For the vast majority of people, meeting the modest RDA of 75-90 mg through a diet rich in fruits and vegetables is the safest and most effective strategy for reaping the benefits of this important antioxidant. Consult a healthcare professional before considering any high-dose supplementation.

For more comprehensive information on the safe use and risks of vitamin C, visit the official page from the National Institutes of Health. NIH Office of Dietary Supplements: Vitamin C Fact Sheet

Frequently Asked Questions

Taking more than 2,000 mg of oral vitamin C can cause unpleasant side effects such as diarrhea, nausea, abdominal cramps, and bloating. Exceeding this amount long-term also increases the risk of kidney stone formation.

The body’s intestinal absorption of vitamin C is limited and becomes inefficient at high doses. At 100g, the vast majority would pass through your system unabsorbed, causing severe digestive distress. Your kidneys would also be overwhelmed trying to excrête the massive excess.

High-dose IV vitamin C is only administered in controlled, medical environments for specific conditions, such as some alternative cancer treatments. It is not approved for general use and carries significant risks, including acute kidney injury, especially for those with existing health issues.

While some foods like blackcurrants and guavas are very high in vitamin C, it is practically impossible and inadvisable to consume the massive quantities required to reach 100g using diet alone. Your body would simply not absorb it efficiently, and it is far beyond what is needed.

The most immediate and common signs of excessive vitamin C intake are gastrointestinal issues, including diarrhea, stomach cramps, and nausea. These symptoms occur as the body tries to expell the unabsorbed excess.

No, more is not always better. While vitamin C is vital for immune function, consuming amounts beyond the RDA does not provide extra benefits for healthy individuals and can lead to adverse effects. The body's tissues become saturated with vitamin C at relatively low intakes, making higher doses largely ineffective.

Research indicates that high-dose vitamin C has, at most, a modest effect on shortening the duration of the common cold by a day or two in some people, but it does not prevent colds. The side effects of megadosing often outweigh any minor benefit.