I do not know which medicines you are taking, but vitamin D supplements can interfere with certain medicines. Its level in the blood can increase. It is better to consult with your doctor before taking the supplement.

These prescribed drugs include:

• Estrogens – Hormone replacement therapy with estrogens can increase vitamin D level in the blood. This has a positive effect on calcium and bone metabolism. This benefit is lost when progesterone is added in the therapy
• Isoniazid – This is a drug used to treat tuberclosis, may raise blood levels of vitamin D
• Thiazide – Diuretics such as hydrochlorothiazide can increase the effect of vitamin D and can lead to very high calcium levels in the blood.
Vitamin D levels may be decreased if you take the following drugs:
• Antacids – long time use can affect the bioavailability of vitamin D
• Calcium channel blockers – These medicines are used to treat the high blood pressure and other heart diseases. They may decrease the production of vitamin D by the body
• Cholestyramine – This decreases the cholesterol. It interferes with the absorption of vitamin D
• Antiepileptic medications such as phenytoin, Phenobarbital and others may accelerate the body’s use of vitamin D
• Weight loss medications – Orlistat binds with fat and thus prevents the absorption of vitamin D and other fat soluble vitamins.
• Vitamin D may enhance the effects of doxorubicin, a drug used in treating cancers
• If you take digoxin, a drug used to treat irregular heart rhythms and vitamin D together, the high level of calcium can increase the drug to toxic ranges
• Corticosteroid drugs such as prednisone, used to reduce inflammation can reduce calcium absorption and impair vitamin D metabolism. This increases the risk for osteoporosis

Never increase the dose of the medicine by yourself. Even if you take food supplements talk to your doctor.