Metformin is a prescription drug that treats high blood sugar levels caused by type 2 diabetes in adults and some children. Part of its mechanism of action is to decrease glucose production in the liver. The effectiveness of this drug may vary based on your medical history and diagnosis.

Boxed warning: Risk of lactic acidosis

Metformin has a boxed warning about the risk of lactic acidosis. A boxed warning is the most serious warning from the Food and Drug Administration (FDA). It alerts doctors and patients about drug effects that may be dangerous.

Lactic acidosis is a rare and life threatening side effect of metformin. It can occur if your body can’t get rid of lactic acid quickly enough. This can cause lactic acid to build up in your blood.

Symptoms of lactic acidosis may include:

If you have any symptoms of lactic acidosis, talk with your doctor right away. If your symptoms are severe or seem life threatening, call 911 or your local emergency number right away or go to the nearest emergency room.

Your risk of lactic acidosis may be higher if you have kidney or liver problems, certain conditions such as heart failure, take certain other drugs, are age 65 years or older, drink large amounts of alcohol, or have certain kinds of procedures done.

To learn more about this warning, talk with your doctor or pharmacist.

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How metformin works

Metformin belongs to a class of medications called biguanides. Metformin is prescribed to treat high blood sugar levels caused by type 2 diabetes. It works by:

  • reducing the amount of glucose (sugar) made by your liver
  • decreasing the amount of glucose your body absorbs
  • increasing the effect of insulin on your body

Insulin is a hormone that helps your body remove extra sugar from your blood. This lowers your blood sugar levels.

If you have questions about how metformin works, talk with your doctor or pharmacist.

How long metformin takes to work

Metformin typically starts to work by lowering blood sugar levels in the first week of treatment. However, it may take 2 to 3 months to see its full effect. You can tell that metformin is working because your blood sugar should be near your target range, as discussed with your doctor. Your symptoms of diabetes should also get better.

Some signs that metformin may be working include lower blood sugar levels after eating (if you test at home), lower glycosylated hemoglobin (A1C) levels, and modest weight loss or no additional weight gain.

If you have questions about how long it takes metformin to work, talk with your doctor.

Disclaimer: Medical News Today has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.