Your body doesn't store vitamin C, so if you consume more than you need, the excess leaves your body with your urine. But people who take extreme doses of vitamin C still might experience negative effects. The minimum recommended daily amount for men ages 19 and older is 90 mg a day, which is a sufficient amount to prevent scurvy and meet your body's other needs. Women over the age of 19 should ingest 75 mg a day.
Some people believe that taking huge doses of vitamin C can prevent colds, which is false. Some studies do show, however, that vitamin C supplements can decrease the duration of a cold, according to the University of Florida Extension Service. If you decide to take more vitamin C than the daily recommended amount, talk to your doctor first to determine a safe dosage.
Although not all people have the same reaction, excessive intake of vitamin C can cause nausea, vomiting, heartburn, diarrhea, abdominal cramps, headache, kidney stones and insomnia. If you experience any of these symptoms, ask your doctor whether you're getting too much vitamin C in your diet.
Pregnant women who consume excessive vitamin C might increase the risk of preterm birth, according to dietitian Melinda Johnson of Baby Center. Although some vitamin C is necessary for preventing scurvy, taking more than 6,000 mg of vitamin C a day while pregnant can cause rebound scurvy in newborn children due to the drastic drop in vitamin C intake they experience after birth, according to the University of Maryland Medical Center. Generally, pregnant women shouldn't take vitamin supplements of any kind without the approval of their medical providers.
The safest approach is to keep your daily vitamin C intake below 2,000 mg, which is considered the upper limit of a safe dosage range. Note that this greatly exceeds the minimum daily requirement of all groups. Most people can obtain all of the vitamin C they need from a balanced diet that includes fruits and vegetables, so vitamin C supplementation is rarely necessary.