Adverse Side Effects of Vitamin D3

Vitamin D is important for maintaining strong bones and teeth and developing a healthy nervous system. Vitamin D3 is only available from sunshine or animal products. Good sources of D3 include seafood, beef liver, cheese and egg yolks. No side effects have been recorded from low doses of vitamin D3, but overdosing can cause serious consequences.

Dosing

A typical vitamin D3 supplement is 25 micrograms (mcg), or 1,000 IU (international units), taken daily. At that level, there are no adverse effects for healthy individuals. Even taking twice the recommended amount for an extended period of time shows no bad effect. The National Institutes of Health indicate that adverse effects begin above 100 mcg, or 4,000 IU, although the American Journal of Clinical Nutrition says that difficulties may not begin until an individual takes 250 mcg, or 10,000 IU, per day.

Mild Effects

Mild effects noticed at the lowest overdose level above 100 mcg are constipation, nausea, vomiting, general weakness, mild dizziness, lethargy and weight loss. An overdose of vitamin D3 can also lead to frequent urination, extreme thirst, nervousness and itching.

Serious Effects

Hypercalcaemia, or high calcium levels, produced by taking large doses of vitamin D, creates high blood pressure, which can lead to heart disease by slowing blood flow to the heart. Calcium deposits from chronically high levels of vitamin D3 can produce kidney and bladder stones. Calcium toxicity can also lead to both anorexia and kidney failure by restricting fluid circulation throughout the body.

Allergic Reactions

Allergic reactions are the only adverse effect created by vitamin D3 not related to overdosing. Rashes, severe dizziness, difficulty breathing, or swelling of the face, tongue, or throat are all signs of an allergy and require immediate medical attention.

Medical History

Vitamin D3 supplements should not be taken by those with certain medical conditions, including pre-existing hypercalcaemia and difficulty absorbing calcium from food. Supplements complicate diseases of the liver, kidney and heart, plus immune system disorders like sarcoidosis. Tell your doctor before taking additional vitamin D if suffering from intestinal or digestive problems, including Crohn's disease, Whipple's disease, little or no stomach acid, or low levels of bile.

Drug Interactions

Side effects may result if someone takes vitamin D3 with blood pressure pills or heart medication. Certain medicines used to treat kidney disease already contain high doses of vitamin D3, and taking D3 supplements can lead to hypercalcaemia. Check to see if antacids or laxatives contain vitamin D before taking them.

References

• Office of Dietary Supplements
• National Center for Biotechnology Information

Resources

• The American Journal for Clinical Nutrition