If you are currently being treated with any of the following medications, you should not use vitamin A without first talking to your healthcare provider.

Antacids
One study suggests that the combination of vitamin A and antacids may be more effective than antacids alone in healing ulcers.

Birth Control Medications
Birth control medications increase the levels of vitamin A in women. Therefore, it may not be appropriate for women taking birth control medications to take vitamin A supplements. Again, this is something that should be discussed with a knowledgeable healthcare provider.

Blood thinning Medications, Anticoagulants
Long-term use of vitamin A or use of high doses may lead to an increased risk of bleeding for those taking blood-thinning medications, particularly warfarin. People taking this medication should notify a doctor before taking vitamin A supplements.

Cholesterol-lowering Medications
The cholesterol-lowering medications cholestyramine and colestipol (both known as bile acid sequestrants), may reduce the body's ability to absorb vitamin A.

Another class of cholesterol-lowering medications called HMG-CoA reductase inhibitors or statins (including atorvastatin, fluvastatin, and lovastatin, among others) may actually increase vitamin A levels in the blood.

Doxorubicin
Test tube studies suggest that vitamin A may enhance the action of doxorubicin, a medication used for cancer. Much more research is needed, however, to know whether this has any practical application for people.

Neomycin
This antibiotic may reduce vitamin A absorption, especially when delivered in large doses.

Omeprazole
Omeprazole (used for gastroesophageal reflux disease or "heart burn") may influence the absorption and effectiveness of beta-carotene supplements. It is not known whether this medication affects the absorption of beta-carotene from foods.

Weight Loss Products
Orlistat, a medication used for weight loss and olestra, a substance added to certain food products, are both intended to bind to fat and prevent the absorption of fat and the associated calories. Because of their effects on fat, orlistat and olestra may also prevent the absorption of fat-soluble vitamins such as vitamin A. Given this concern and possibility, the Food and Drug Administration (FDA) now requires that vitamin A and other fat soluble vitamins (namely, D, E, and K) be added to food products containing olestra. How well vitamin A from such food products is absorbed and used by the body is not clear. In addition, physicians who prescribe orlistat add a multivitamin with fat soluble vitamins to the regimen.

Alcohol
Alcohol can enhance the toxic effects of vitamin A, presumably through its adverse effects on the liver. It is unwise to take vitamin A if you drink regularly.