Generic Name: Metformin Brand Name(s): Generics only. No brands available.

Know the basics

What is metformin used for?

Metformin is used with a proper diet and exercise program and possibly with other medications to control high blood sugar. It is used in patients with type 2 diabetes. Controlling high blood sugar helps prevent kidney damage, blindness, nerve problems, loss of limbs, and sexual function problems. Proper control of diabetes may also lessen your risk of a heart attack or stroke. Metformin works by helping to restore your body’s proper response to the insulin you naturally produce. It also decreases the amount of sugar that your liver makes and that yourstomach/intestines absorb.

This section contains uses of this drug that are not listed in the approved professional labeling for the drug but that may be prescribed by yourhealth care professional. Use this drug for a condition that is listed in this section only if it has been so prescribed by your health care professional.

Metformin may be used with lifestyle changes such as diet and exercise to prevent diabetes in people who are at high risk for becoming diabetic. It is also used in women with a certain disease of the ovaries (polycystic ovarian syndrome). Metformin may make menstrual cycles more regular and increase fertility.

How should I take metformin?

Take this medication by mouth as directed by your doctor, usually 1-3 times a day with meals. Drink plenty of fluids while taking this medication unless otherwise directed by your doctor.

The dosage is based on your medical condition, kidney function, and response to treatment. Your doctor may direct you to take a low dose of this medication at first, gradually increasing your dose to lower the chance of side effects such as upset stomach. Your doctor will adjust your dose based on your blood sugar levels to find the best dose for you. Follow your doctor’s directions carefully.

Take this medication regularly in order to get the most benefit from it. Remember to use it at the same times each day.

If you are already taking another anti-diabetic drug (such as chlorpropamide), follow your doctor’s directions carefully for stopping/continuing the old drug and starting metformin.

Check your blood sugar regularly as directed by your doctor. Keep track of the results, and share them with your doctor. Tell your doctor if your blood sugar measurements are too high or too low. Your dosage/treatment may need to be changed.

How do I store metformin?

Medication is best stored at room temperature away from direct light and moisture. To prevent drug damage, you should not store medication in the bathroom or the freezer. There may be different brands of medication that may have different storage needs. It is important to always check the product package for instructions on storage, or ask your pharmacist. For safety, you should keep all medicines away from children and pets.

You should not flush medication down the toilet or pour them into a drain unless instructed to do so. It is important to properly discard this product when it is expired or no longer needed. Consult your pharmacist for more details about how to safely discard your product.

Know the precautions & warnings

What should I know before using metformin?

Before taking metformin,

  • Tell your doctor and pharmacist if you are allergic to metformin, any of the ingredients of metformin liquid or tablets, or any other medications. Ask your pharmacist or check the manufacturer’s patient information for a list of the ingredients.
  • Tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking. Be sure to mention any of the following: acetazolamide(diamox); amiloride (midamor, in moduretic); angiotensin-converting enzyme (ace) inhibitors such as benazepril (lotensin), captopril (capoten), enalapril (vasotec), fosinopril (monopril), lisinopril (prinivil, zestril), moexipril (univasc), perindopril (aceon), quinapril (accupril), ramipril (altace), and trandolapril (mavik); beta-blockers such as atenolol (tenormin), labetalol (normodyne), metoprolol (lopressor, toprol xl), nadolol (corgard), and propranolol (inderal); calcium channel blockers such as amlodipine (norvasc), diltiazem (cardizem, dilacor, tiazac, others), felodipine (plendil), isradipine (dynacirc), nicardipine (cardene), nifedipine (adalat, procardia), nimodipine (nimotop), nisoldipine (sular), and verapamil (calan, isoptin, verelan); cimetidine (tagamet); digoxin (lanoxin); diuretics (‘water pills’); furosemide (lasix); hormone replacement therapy; insulin or other medications for diabetes; isoniazid; medications for asthma and colds; medications for mental illness and nausea; medications for thyroid disease; morphine (ms contin, others); niacin; oral contraceptives (‘birth control pills’); oral steroids such as dexamethasone (decadron, dexone), methylprednisolone (medrol), and prednisone (deltasone); phenytoin (dilantin, phenytek); procainamide (procanbid); quinidine; quinine; ranitidine (zantac); topiramate (topamax); triamterene (dyazide, maxzide, others); trimethoprim (primsol); vancomycin (vancocin); or zonisamide (zonegran). Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
  • Tell your doctor if you have or have ever had any medical condition.
  • Tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking metformin, call your doctor.
  • Tell your doctor if you eat less or exercise more than usual. This can affect your blood sugar. Your doctor will give you instructions if this happens.

Is it safe to take metformin during pregnancy or breast-feeding?

There are no adequate studies in women for determining risk when using this medication during pregnancy or while breastfeeding. Please always consult with your doctor to weigh the potential benefits and risks before taking this medication. This medication is pregnancy risk category B according to the US Food and Drug Administration (FDA).

FDA pregnancy risk category reference below:

  • A=No risk,
  • B=No risk in some studies,
  • C=There may be some risk,
  • D=Positive evidence of risk,
  • X=Contraindicated,
  • N=Unknown

Know the side effects

What are the side effects of metformin?

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

This medication may cause lactic acidosis (a build-up of lactic acid in the body, which can be fatal). Lactic acidosis can start slowly and get worse over time. Get emergency medical help if you have even mild symptoms of lactic acidosis, such as:

  • Muscle pain or weakness;
  • Numb or cold feeling in your arms and legs;
  • Trouble breathing;
  • Feeling dizzy, light-headed, tired, or very weak;
  • Stomach pain, nausea with vomiting;
  • Slow or uneven heart rate.

Call your doctor at once if you have any other serious side effect such as:

  • 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 nausea, vomiting, diarrhea, gas, stomach pain.

Not everyone experiences these side effects. There may be some side effects not listed above. If you have any concerns about a side-effect, please consult your doctor or pharmacist.

Know the interactions

What drugs may interact with metformin?

Medication may interact with other drugs that you are currently taking, which can change how your drug works or increase your risk for serious side effects. To avoid any potential drug interactions, you should keep a list of all the drugs you are using (including prescription drugs, nonprescription drugs and herbal products) and share it with your doctor and pharmacist. For your safety, do not start, stop, or change the dosage of any drugs without your doctor’s approval, especially:

  • 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 (Quin-G) or quinine (Qualaquin);
  • Trimethoprim (Proloprim, Primsol, Bactrim, Cotrim, Septra); or
  • Vancomycin (Vancocin, Lyphocin).

You may be more likely to have hyperglycemia (high blood sugar) if you take metformin with other drugs that can raise blood sugar, such as:

  • Isoniazid;
  • Diuretics (water pills);
  • Steroids (prednisone and others);
  • Heart or blood pressure medication (cartia, cardizem, covera, isoptin, verelan, and others);
  • Niacin (advicor, niaspan, niacor, simcor, slo-niacin, 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.

Does food or alcohol interact with metformin?

Medication may interact with food or alcohol by altering the way the drug works or increase the risk for serious side effects. Please discuss with your doctor or pharmacist any potential food or alcohol interactions before using this drug.

What health conditions may interact with metformin?

Medication may interact with your health condition. This interaction may worsen your health condition or alter the way the drug works. It is important to always let your doctor and pharmacist know all the health conditions you currently have, especially:

  • Alcohol, excessive use;
  • Underactive adrenal glands;
  • Underactive pituitary gland;
  • Undernourished condition;
  • Weakened physical condition;
  • Any other condition that causes low blood sugar—Patients with these conditions may be more likely to develop low blood sugar while taking metformin.
  • Anemia (low levels of red blood cells) ;
  • Vitamin B12 deficiency—Use with caution. May make these conditions worse.
  • Congestive heart failure, acute or unstable;
  • Dehydration;
  • Heart attack, acute;
  • Hypoxemia (decreased oxygen in the blood);
  • Kidney disease;
  • Liver disease;
  • Sepsis (blood poisoning);
  • Shock (low blood pressure, blood circulation is poor)—A rare condition called lactic acidosis can occur. Talk with your doctor if you have concerns about this.
  • Diabetic ketoacidosis (ketones in the blood);
  • Kidney disease, severe;
  • Metabolic acidosis (extra acids in the blood);
  • Type 1 diabetes—Should not be used in patients with these conditions.
  • Fever;
  • Infection;
  • Surgery;
  • Trauma—These conditions may cause temporary problems with blood sugar control and your doctor may want to treat you with insulin.

Understand the dosage

The information provided is not a substitute for any medical advice. You should ALWAYS consult with your doctor or pharmacist before using this medication.

What is the dose of medication for an adult?

Usual Adult Dose for Diabetes Type 2

  • Immediate-release:
  • Initial dose: 500 mg orally twice a day or 850 mg orally once a day
  • Dose titration: Increase in 500 mg weekly increments or 850 mg every 2 weeks as tolerated
  • Maintenance dose: 2000 mg daily
  • Maximum dose: 2550 mg daily
  • Extended-release:
  • Initial dose: 500 to 1000 mg orally once a day
  • Dose titration: Increase in 500 mg weekly increments as tolerated
  • Maintenance dose: 2000 mg daily
  • Maximum dose: 2500 mg daily

What is the dose of medication for a child?

Usual Pediatric Dose for Diabetes Type 2: 10 years or older:

  • Immediate-release:
  • Initial dose: 500 mg orally twice a day
  • Dose titration: Increase in 500 mg weekly increments as tolerated
  • Maintenance dose: 2000 mg daily
  • Maximum dose: 2000 mg daily

How is medication available?

Medication is available in the following dosage forms and strengths:

Tablet Extended Release, Oral: 500 mg, 1000 mg.

What should I do in case of an emergency or overdose?

In case of an emergency or an overdose, call your local emergency services or go to your nearest emergency room.

What should I do if I miss a dose?

If you miss a dose of medication, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and take your regular dose as scheduled. Do not take a double dose.

Hello Health Group does not provide medical advice, diagnosis or treatment.

Review Date: January 4, 2017 | Last Modified: January 4, 2017