Isoniazid is on the leaflet's list of medicines that can interfere with how well Glipizide controls your blood sugar. The list also includes water tablets (diuretics), steroids, thyroid medicines, oestrogens, birth control pills, phenytoin, nicotinic acid and calcium channel blockers. If you take both, tell your doctor or pharmacist so they can keep an eye on your blood sugar.
These medicines are often taken together with some care. Your doctor may change a dose, space them apart or check on you more often. Make sure your doctor and pharmacist know you take both.