Taking any medication or supplement in excess can cause side effects, including Vitamin C. Even though Vitamin C is a water-soluble vitamin and excess amounts are typically eliminated through the urine, "mega doses" of Vitamin C containing supplements may cause headache, diarrhea, nausea, vomiting, and abdominal cramps.
Additionally, some patients may experience a higher risk of developing kidney stones after large doses of ascorbic acid. This may be more likely in patients with kidney disease, a history of kidney stones, and children under 2 years old.
Vitamin C Information
Vitamin C, also known as ascorbic acid, is found in a variety of foods including many fruits and vegetables. It is especially potent in citrus fruits and green peppers. Vitamin C is an antioxidant that is thought to help prevent heart disease, stroke, and cancer. It may have beneficial effects on wound healing, the common cold, and has even shown some evidence in patients with sepsis.
Vitamin C is also well known as the treatment for scurvy, a condition that was somewhat common with sailors who spent months at sea. Vitamin C is important to obtain via diet or supplements because we cannot make it ourselves.
Vitamin C Dosing
The Recommended Dietary Allowances for Vitamin C
For all adults, the maximum recommended dose of oral Vitamin C is 2000 mg. Doses up to 6 g daily has been used occasionally, but wouldn’t be recommended without the advice of a physician.
Additionally, IV ascorbic acid has been used at substantially higher doses in select patients including sepsis. While the evidence is not robust in septic patients, one small study showed a reduction in mortality by utilizing ascorbic acid IV 1.5 g every 6 hours in combination with hydrocortisone and thiamine.
The bottom line is that Vitamin C has many beneficial effects and is unlikely to cause harm in most patients. However, taking "mega doses" of Vitamin C could lead to nausea, vomiting, diarrhea, headache, abdominal cramping, and higher risk of kidney stones.
If taking more than the recommended maximum dose of 2000 mg daily, it is important to understand the risks and discuss with your physician.