• Basic Info
• Top Questions
• Clinical Info
• Interactions

You may be more likely to have hyperglycemia (high blood sugar) if you are taking metformin with other drugs that raise blood sugar. Drugs that can raise blood sugar include:

• isoniazid;

• diuretics (water pills);

• steroids (prednisone and others);

• phenothiazines (Compazine and others);

• thyroid medicine (Synthroid and others);

• birth control pills and other hormones;

• seizure medicines (Dilantin and others); and

• diet pills, or medicines to treat asthma, colds or allergies.

You may be more likely to have hypoglycemia (low blood sugar) if you are taking metformin with other drugs that lower blood sugar. Drugs that can lower blood sugar include:

• some nonsteroidal anti-inflammatory drugs (NSAIDs);

• aspirin or other salicylates (including Pepto-Bismol);

• sulfa drugs (Bactrim and others);

• a monoamine oxidase inhibitor (MAOI);

• beta-blockers (Tenormin and others); or

• probenecid (Benemid).

Some medications may interact with metformin. Tell your doctor if you are using any of the following drugs:

• furosemide (Lasix);

• nifedipine (Adalat, Procardia);

• cimetidine (Tagamet) or ranitidine (Zantac);

• amiloride (Midamor) or triamterene (Dyrenium);

• digoxin (Lanoxin);

• morphine (MS Contin, Kadian, Oramorph);

• procainamide (Procan, Pronestyl, Procanbid);

• quinidine (Cardioquin, Quinidex, Quinaglute);

• trimethoprim (Proloprim, Primsol, Bactrim, Cotrim, Septra); or

• vancomycin (Vancocin, Lyphocin).

This list is not complete and there may be other drugs that can interact with metformin. Tell your doctor about all the prescription and over-the-counter medications you use. This includes vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start using a new medication without telling your doctor.

Get emergency medical help if you have any of these symptoms of lactic acidosis: weakness, increasing sleepiness, slow heart rate, cold feeling, muscle pain, shortness of breath, stomach pain, feeling light-headed, and fainting.

Stop using metformin and get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have any of these serious side effects:

• feeling short of breath, even with mild exertion;

• swelling or rapid weight gain; or

• fever, chills, body aches, flu symptoms.

Less serious side effects may include:

• headache or muscle pain;

• weakness; or

• mild nausesa, vomiting, diarrhea, gas, stomach pain.

This is not a complete list of side effects and others may occur. Tell your doctor about any unusual or bothersome side effect.