Vitamin D is a fat-soluble vitamin required for the maintenance of healthy bones and other important biological processes. Supplements containing vitamin D are used to treat a variety of health conditions, including osteoporosis. You should consult your doctor before taking vitamin D, because overdosing on vitamin D supplements can cause several side effects, some of which may be severe.
Overdose Levels
Many vitamin D supplements contain 400 International Units, abbreviated IU, per pill. The Institute of Medicine has set a tolerable upper intake level of 4,000 IU per day for adolescents and children older than 9 years. The tolerable upper intake level is 3,000 IU for children 4 to 8 years old; 2,500 IU for children 1 to 3 years old; 1,500 IU for infants 7 to 12 months old and 1,000 IU for infants 0 to 6 months old. The tolerable upper intake level is the maximum amount that should be taken in order to avoid symptoms of toxicity. However, some health care providers think that doses up to 10,000 IU per day are generally safe, reports the Office of Dietary Supplements of the National Institutes of Health. Common doses used to treat diseases range from 400 to 1,200 IU per day. You should ask your doctor about the right dose of vitamin D you should take to meet your individual health needs and avoid overdosing.
Gastrointestinal Symptoms of Overdose
An overdose of vitamin D may cause several symptoms affecting the gastrointestinal system. Upset stomach, nausea, dry mouth and loss of appetite are often early symptoms of a vitamin D overdose. Some individuals may experience an unusual metallic taste in their mouth. Long-term exposure to high vitamin D levels may result in anorexia and unintended weight loss.
Raised Calcium Levels
Vitamin D regulates how much calcium the body absorbs from food, and overdosing on vitamin D supplements can raise levels of calcium in the blood to dangerously high levels. When calcium levels are elevated, calcium deposits can form in tissues throughout the body. Calcification of the blood vessels can contribute to atherosclerosis, or hardening of the arteries. Calcification of the heart or other internal organs can damage these organs, leading to heart disease or other health conditions such as liver disease. The formation of calcium deposits in the kidneys can raise the risk of kidney stones.
Additional Symptoms
Large doses of vitamin D can cause several other nonspecific symptoms, including muscle weakness, fatigue, excess sleepiness and headache. Excessive thirst may develop, as well as excess urine production. In certain cases, heart arrhythmias may also occur. Overdosing on vitamin D may also cause the liver to metabolize other prescription drugs faster than normal, which can decrease the effectiveness of these drugs, including cyclosporine, triazolam, lovastatin and estrogen.
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