How Much Vitamins Are Too Much?

If you consume excess amounts of a particular vitamin, it can disrupt your body processes and cause adverse physical symptoms. This is referred to as a vitamin toxicity. Not all vitamins are harmful in high amounts, however. The Food and Nutrition Board provides an upper tolerable intake level, or UL, for the vitamins that pose a risk in excess amounts. The UL represents the highest amount of a particular vitamin that can be consumed without causing any health problems.

Vitamin A

Because the body is able to store vitamin A, consuming excess amounts of the vitamin either through food or supplements can cause adverse health effects. "Nutrition and You" by Joan Salge Blake notes that most vitamin A toxicity occurs as a result of consuming too much vitamin A through supplements, however. If you consume too much vitamin A in the form of carotenoids, it can lead to a harmless condition called carotenodermia, which is characterized by orange tint to the skin. Excess vitamin A consumption can also lead to liver toxicity, which can be fatal. The UL for vitamin A is set at 3,000 mg daily.

Vitamin E

There are no known adverse health effects from consuming too much dietary vitamin E, but excess supplementation can increase your risk of severe bleeding and hemorrhaging. In order to avoid this, the upper limit for vitamin E has been set at 1,000 mg daily.

Vitamin D

Excess vitamin D consumption can lead to nausea, vomiting, loss of appetite and constipation. If you regularly consume too much vitamin D, it can lead to a condition called hypervitaminosis D, which causes an increase in calcium absorption. This can lead to a life-threatening condition in which calcium levels in the blood accumulate to dangerous levels. The upper level for vitamin D has been set at 2,000 IU per day.

Niacin

There are no known risks of consuming too much niacin in your diet. Excess niacin supplementation, however, has been shown to cause flushing of the face and chest, nausea, vomiting and an increase in blood sugar levels. Excess niacin can also lead to liver damage. The upper limit for niacin is 35 mg.

Vitamin B-6

Too much vitamin B-6 can lead to nerve damage. It is possible to consume excess vitamin B-6 through foods and supplementation, so the upper limit has been set at 100 mg daily.

Folic Acid

The upper limit for folic acid applies to supplements and synthetic folic acid only. Although folate is not toxic, consuming too much folic acid in these forms can cover up the symptoms of a vitamin B-12 deficiency and can lead to permanent nerve damage. Because of this, the Food and Nutrition Board has set an upper limit for folic acid at 1,000 mcg.

Vitamin C

Excess amounts of vitamin C are not toxic, but they can cause uncomfortable symptoms such as nausea, stomach cramps and diarrhea. Excess vitamin C can also increase your risk of developing kidney stones. The upper limit for vitamin C is 2,000 mg daily.