What is Metformin: Uses, Warnings & Interactions

Take your medicine as directed. Your dose may need to be changed several times to find what works best for you.

Read the medication guide and follow the patient instructions that come with this medicine. Talk to your doctor or pharmacist if you have any questions.

Try to take this medicine with food or milk to decrease the likelihood of stomach upset.

Swallow the tablets whole.

Measure the oral liquid medicine with the measuring cup that comes with the medicine.

Store this medicine at room temperature.

Ask a doctor what to do if a dose of metformin is missed.

Unless instructed otherwise by a doctor, a missed dose should be skipped. Take the next dose as scheduled.

Do not take extra medicine to make up for a missed dose.

This medicine is not right for everyone. 

Do not use it if you have had an allergic reaction to metformin.

People with severe kidney disease cannot safely take metformin.

Metformin should never be taken by people with metabolic acidosis or diabetic ketoacidosis.

Tell any doctor or other healthcare provider who treats you that you are using this medicine.

You may need to stop using this medicine before you have surgery, an x-ray, CT scan, or other medical test.

Your doctor or healthcare provider may need to check your blood sugar, kidney function, and other effects of this medicine at regular visits. Keep all appointments.

Metformin can cause a serious condition called lactic acidosis. Though rare, it’s more likely to happen in:

• Seniors

• People with kidney problems or liver problems

• People with low oxygen levels (such as people with heart failure or following a heart attack)

• People who are dehydrated

• People who drink alcohol excessively

• People taking certain types of drugs

• People undergoing surgery or medical scans with contrast dye

Tell your doctor if you have:

• A history of diabetic ketoacidosis or metabolic acidosis

• Kidney disease

• Liver disease

• Heart problems including heart failure

• Vitamin B12 deficiency

• Anemia

• Hormone disorders

• Any other medical condition

The doctor will need to know if you drink alcohol.

Tell your doctor if you’re pregnant, breastfeeding, or making plans to become pregnant or breastfeed.

This medicine may cause some premenopausal women who do not have regular monthly periods to ovulate. This can increase the chance of pregnancy. If you are a woman of childbearing potential, discuss birth control options with your doctor.

The doctor may advise a vitamin B12 supplement while taking this medicine.

Because of possible drug interactions, tell the prescribing healthcare provider about all prescription drugs, over-the-counter medicines, and supplements you are using before taking this drug.

Tell other healthcare providers you are using this medicine before they prescribe new medications.

Some medicines can affect how metformin works or increase the risk of side effects. Tell your doctor if you are using any of the following:

• Insulin

• Diabetes drugs that increase the body’s secretion of insulin

• Drugs that make you pee (diuretics)

• Corticosteroids

• Thyroid hormones

• Estrogens (either birth control pills or hormone replacement)

• Blood pressure drugs called calcium channel blockers

• A type of drug that treats psychosis and similar disorders called phenothiazines

• icotinic acid, or isoniazid

• The antiseizure drugs topiramate, zonisamide, or phenytoin 

• The glaucoma drug acetazolamide

• Nicotinic acid, isoniazid, or dichlorphenamide

Some drugs slow down the body’s metabolism of metformin and increase the risk of side effects. Tagamet (cimetidine) is one such drug. If these drugs are combined with trazodone, doses may need to be modified. 

Avoid drinking alcohol while you are using this medicine. Do not drink excessive amounts of alcohol. That includes chronic drinking and binge drinking.