What Happens If You Take 7000 mg of Vitamin C?

January 7, 2026 •

4 min read

The Tolerable Upper Intake Level (UL) for vitamin C in adults is 2,000 mg per day, making a 7,000 mg dose significantly higher than the recommended maximum intake. Exceeding this limit is not life-threatening for most people but can cause a range of unpleasant side effects as the body struggles to process the excess amount.

Quick Summary

Taking 7000 mg of vitamin C can cause significant gastrointestinal issues like diarrhea, cramps, and nausea, along with increasing the risk of kidney stones. The body cannot absorb the excessive amount, and most is excreted. Higher doses are particularly dangerous for individuals with certain health conditions, including kidney disease and hemochromatosis.

Key Points

Gastrointestinal Distress: Taking 7000 mg of vitamin C will very likely cause significant diarrhea, stomach cramps, nausea, and bloating.
Kidney Stone Risk: The body converts excess vitamin C into oxalate, increasing the likelihood of forming calcium oxalate kidney stones, especially for those with existing kidney issues.
Inefficient Absorption: The body's ability to absorb vitamin C is limited, so most of the 7000 mg dose will not be utilized and will instead be excreted in urine.
Iron Overload Danger: For individuals with hemochromatosis, a high vitamin C dose can worsen iron accumulation and cause serious tissue damage.
No Added Health Benefits: Consuming a dose far beyond the 2,000 mg daily upper limit offers no proven benefits and primarily increases the risk of side effects.
Tolerable Upper Limit: The recommended maximum daily intake for vitamin C is 2,000 mg for adults. A 7,000 mg dose is more than triple this amount.

The Science Behind Water-Soluble Vitamins

Vitamin C, or ascorbic acid, is a water-soluble vitamin, which means it dissolves in water and is not stored in the body's tissues. This is why a regular intake from diet or supplements is necessary. However, this also means that when you consume more than your body can absorb and utilize, the excess is flushed out through your urine. While this reduces the risk of serious, fat-soluble vitamin toxicity, it does not mean that megadoses are harmless. The journey of that excess vitamin C through your digestive and urinary systems is what causes most of the immediate side effects.

Immediate Side Effects: Gastrointestinal Distress

One of the most common and immediate consequences of taking a high dose like 7,000 mg of vitamin C is severe gastrointestinal upset. The high concentration of the unabsorbed vitamin in your gut can have a strong osmotic effect, pulling water into your intestines and leading to significant discomfort.

Diarrhea: This is perhaps the most well-known symptom of megadose vitamin C. It is a direct result of the unabsorbed ascorbic acid drawing fluid into the colon.
Abdominal Cramping: The digestive system's protest against the overload manifests as painful stomach cramps and general abdominal discomfort.
Nausea and Bloating: Many individuals will experience intense nausea, which can lead to vomiting, along with a feeling of fullness and bloating.
Heartburn: As a highly acidic substance, a large quantity of vitamin C can also cause heartburn or a burning sensation in the esophagus.

Potential Long-Term Risks of Habitual Megadosing

While a single dose is unlikely to cause permanent damage in a healthy person, repeatedly taking such high amounts can lead to more serious health concerns, especially in those with predispositions. The Tolerable Upper Intake Level is set at 2,000 mg per day for a reason. Long-term, high-dose usage can exacerbate certain pre-existing conditions.

Kidney Stones: The metabolism of vitamin C produces oxalate, a waste product that is excreted in the urine. At high doses, this can increase urinary oxalate levels, potentially leading to the formation of calcium oxalate kidney stones, a particular risk for those with a history of kidney issues.
Iron Overload (Hemochromatosis): Vitamin C significantly increases the body's absorption of non-heme iron (iron from plant-based sources). For most people, this is beneficial. However, for those with hereditary hemochromatosis, a condition causing the body to store excessive iron, a megadose of vitamin C can worsen iron accumulation and cause serious tissue damage.
Dental Enamel Erosion: Frequent consumption of high-dose chewable vitamin C can wear down dental enamel over time due to its acidic nature, leading to tooth sensitivity and a higher risk of cavities.
Interference with Medical Tests: Extremely high levels of vitamin C can interfere with certain lab tests, including blood glucose screening and tests for occult blood in stool. This can lead to misleading diagnostic results.

Comparison: Safe Intake vs. Megadose (7000 mg)


Feature	Safe Daily Intake (75-90 mg)	Megadose (7000 mg)
Absorption	Very efficient. The body absorbs the majority of the vitamin.	Highly inefficient. Only a small fraction is absorbed; the rest is excreted.
Health Effects	Supports immune function, collagen production, and antioxidant activity.	May cause side effects; no proven added benefit for most.
Gastrointestinal Symptoms	None, or minimal in sensitive individuals.	High risk of severe diarrhea, nausea, and cramping.
Kidney Risk	No increased risk in healthy individuals.	Increases urinary oxalate, raising kidney stone risk, especially in prone individuals.
Iron Absorption	Enhances absorption, beneficial for those with anemia.	Can cause dangerous iron overload in those with hemochromatosis.
Therapeutic Use	Meets daily nutritional needs.	Intravenous megadoses are sometimes used in a clinical setting for specific conditions under strict medical supervision.

How the Body Handles the Excess

When you ingest 7,000 mg of vitamin C, the body's absorptive mechanisms become saturated. Normally, vitamin C is absorbed in the small intestine via specific transport proteins. These transporters can only move a limited amount of the vitamin at any one time. Once this capacity is exceeded, the unabsorbed vitamin C continues its journey to the large intestine.

Transport Saturation: The body's ability to transport vitamin C from the gut into the bloodstream is finite. This means that after a certain point (typically above 400 mg at one time), the absorption rate drops significantly.
Osmotic Diarrhea: The high concentration of unabsorbed ascorbic acid in the intestines creates an osmotic gradient. This pulls water from the body into the gut, leading to diarrhea.
Renal Excretion: The excess vitamin C that is absorbed is quickly filtered out of the blood by the kidneys and excreted in the urine. This is why overdose is usually not life-threatening but can still strain the kidneys.
Oxalate Formation: A byproduct of vitamin C metabolism is oxalate. While normally harmless, a continuous high level of vitamin C can lead to high concentrations of oxalate in the urine, a known risk factor for calcium oxalate kidney stones.

Conclusion

While a single 7,000 mg dose of vitamin C is highly unlikely to be fatal, it is certainly not a benign event. The immediate consequences will almost certainly include significant gastrointestinal distress, such as diarrhea, cramping, and nausea, as the body attempts to excrete the massive excess. For individuals with underlying health conditions, particularly kidney disorders or hemochromatosis, a dose this high can pose a more serious threat over time, including the risk of kidney stone formation and iron overload. Megadosing beyond the established tolerable upper limit of 2,000 mg offers no proven additional health benefits for the average person. Your body is designed to absorb what it needs and dispose of the rest, but doing so with such a large quantity is a strenuous and uncomfortable process. Always consult a healthcare provider before taking large doses of any supplement.

Disclaimer

This article is for informational purposes only and does not constitute medical advice. Consult a qualified healthcare professional before taking vitamin C supplements, especially in high doses, to discuss any health concerns and determine an appropriate dosage based on your individual needs.

Frequently Asked Questions

While unlikely to be life-threatening for most healthy individuals, taking 7000 mg of vitamin C is not recommended and is considered dangerous for people with certain medical conditions, such as kidney disease or hereditary hemochromatosis. It will cause severe and uncomfortable side effects.

The most common side effects of a 7000 mg vitamin C dose are severe gastrointestinal issues, including diarrhea, abdominal cramps, nausea, and bloating. These occur as the unabsorbed excess vitamin C draws water into the intestines.

The Tolerable Upper Intake Level (UL) for adults is 2,000 mg per day. Regularly exceeding this amount is considered too much and increases the risk of adverse side effects, including kidney stones and digestive upset.

Yes, taking high doses of vitamin C can increase the amount of oxalate in your urine. This can lead to the formation of calcium oxalate kidney stones, particularly in individuals with a history of kidney issues.

Vitamin C is a water-soluble vitamin, meaning it dissolves in water. Your body's absorption capacity for vitamin C is limited, and any excess that is absorbed is efficiently filtered out of the blood by the kidneys and removed through urination.

When the amount of vitamin C overwhelms the body's absorption capacity, the unabsorbed vitamin remains in the intestines. Its osmotic properties draw water into the gut, leading to diarrhea and other digestive issues.

It is extremely difficult, if not impossible, to consume 7000 mg of vitamin C from food sources alone. Side effects from excess vitamin C are almost exclusively associated with high-dose supplements, not dietary intake.