Metformin (By mouth)


Metformin (met-FOR-min)
Used with diet and exercise to control blood sugar in patients with type 2 diabetes. May be used by itself or with other medicines.

Brand Name(s)

There may be other brand names for this medicine.

Glucophage, Glucophage XR, Metformin HCl, Metformin Hydrochloride, Fortamet, Glumetza, AvPak Metformin Hydrochloride, Riomet

When This Medicine Should Not Be Used

You or your child should not use this medicine if you have had an allergic reaction to metformin, or if you have metabolic acidosis (diabetic ketoacidosis) or kidney disease.

How to Use This Medicine

Tablet, Long Acting Tablet, Liquid
  • Your doctor will tell you how much of this medicine to use and how often. Your dose may need to be changed several times in order to find out what works best for you. Do not use more medicine or use it more often than your doctor tells you to.
  • Carefully follow your doctor's instructions about any special diet.
  • Drink extra fluids so you will pass more urine while you are using this medicine. This will keep your kidneys working well and help prevent kidney problems.
  • It is best to take this medicine with food or milk.
  • Swallow the extended-release tablet whole. Do not crush, break, or chew it. Tell your doctor if you have trouble swallowing the tablets whole.
  • While taking the extended-release form of this medicine, part of the tablet may pass into your stools. This is normal and is nothing to worry about.
  • Measure the oral liquid medicine with a marked measuring spoon, oral syringe, or medicine cup.
If a dose is missed:
  • If you miss a dose or forget to use your medicine, use it as soon as you can. If it is almost time for your next dose, wait until then to use the medicine and skip the missed dose. Do not use extra medicine to make up for a missed dose.

How to Store and Dispose of This Medicine

  • Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light.
  • Ask your pharmacist, doctor, or health caregiver about the best way to dispose of any outdated medicine or medicine no longer needed.
  • Keep all medicine away from children and never share your medicine with anyone.

Drugs and Foods to Avoid

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.
  • Many other drugs can interact with metformin. Make sure your doctor knows about all other medicines you are using, especially birth control pills, cold or allergy medicine, estrogen, or any heart medicine. Your doctor will need to know if you are using isoniazid, diuretics (water pills), or steroids such as prednisone or Medrol®. Also tell your doctor if you are using cimetidine (Tagamet®), nicotinic acid (niacin), thyroid medicine, vancomycin (Vancocin®, Vancoled®), or phenytoin (Dilantin®).
  • Tell your doctor if you are also using nifedipine (Procardia®, Adalat®), amiloride (Midamor®), digoxin (Lanoxin®, Digitek®), morphine, procainamide (Procanbid®), quinidine, ranitidine (Zantac®), triamterene (Dyrenium®), or trimethoprim (Proloprim®, Trimpex®).
  • Do not drink alcohol while you are using this medicine.

Warnings While Using This Medicine

  • Make sure your doctor knows if you or your child are pregnant or breastfeeding, or if you have liver disease, heart disease (such as congestive heart failure), or a history of a heart attack or stroke. Tell your doctor if you or your child get an infection while you are using this medicine. Some signs of infection are fever, chills, a cough that will not go away, or a stuffy nose.
  • Make sure any doctor or dentist who treats you knows that you are using this medicine. You may need to stop using this medicine several days before having surgery or medical tests. This medicine may interact with the dye used for an X-ray or CT scan.
  • Do not give this medicine to your child unless your doctor tells you to.
  • Your doctor will need to check your blood or urine at regular visits while you are using this medicine. Be sure to keep all appointments.
  • If your blood sugar gets too low, you may feel weak, drowsy, confused, anxious, or very hungry. You may also sweat, shake, or have blurred vision, a fast heartbeat, or a headache that will not go away. If you have symptoms of low blood sugar (hypoglycemia), check your blood sugar. If your blood sugar is 70 mg/dL (milligrams per deciliter) or below, do one of the following: Drink 4 ounces (one-half cup) of fruit juice, or eat 5 to 6 pieces of hard candy, or take 2 to 3 glucose tablets. Recheck your blood sugar 15 minutes later. If your blood sugar goes above 70 mg/dL, eat a snack or a meal. If your blood sugar is still below 70 mg/dL, drink one-half cup juice, or eat 5 to 6 pieces of candy, or take 2 to 3 glucose tablets. Carry candy or some type of sugar with you at all times, especially if you are away from home. You can take this if you feel that your blood sugar is too low, even if you do not have a blood glucose meter. Always carefully follow your doctor's instructions about how to treat your low blood sugar. Learn what to do if your blood sugar gets too low. Teach friends, coworkers, and family members what they can do to help if you have low blood sugar.
  • This medicine may cause a rare but serious condition called lactic acidosis in some people. Call your doctor right away if you get sick, especially if you have unusual tiredness, weakness, muscle pain, trouble breathing, fever, or nausea. Your risk of getting this condition is greater the longer you take this medicine.

Possible Side Effects While Using This Medicine

Call your doctor right away if you notice any of these side effects:
  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing.
  • Chest discomfort, or unusually slow, fast, or uneven heartbeat.
  • Dry mouth, increased thirst, confusion, or decrease in how much you urinate.
  • Extreme weakness, tiredness, or confusion.
  • Fever or chills.
  • Lightheadedness or fainting.
  • Muscle weakness or pain.
  • Rapid breathing, or trouble breathing.
  • Stomach pain, nausea and vomiting, or diarrhea.
If you notice these less serious side effects, talk with your doctor:
  • Headache.
  • Metallic taste in your mouth.
  • Mild stomach pain or upset, nausea, or gas.

If you notice other side effects that you think are caused by this medicine, tell your doctor

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088
Review Date: 2011-02-04 Reviewed By: Keywords: ,
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