Home > Patients & Visitors > Health Library > Biguanides (Metformin) for Prediabetes and Type 2 Diabetes
Sometimes metformin is combined with other diabetes medicines in one pill. For example:
Biguanides lower blood sugar by:
Metformin does not cause the pancreas to produce more
insulin. It should not cause low blood sugar
(hypoglycemia) or weight gain, unless it is taken in combination with medicines that do. Some people may lose
weight when starting this medicine.
These medicines are used to treat insulin resistance common to people with prediabetes, type 2 diabetes, and polycystic ovarian syndrome.
Type 2 diabetes is a disease that can get worse over time, so medicines may need to change.
Diabetes medicines work best for people who are being active and eating healthy foods. Studies have suggested that metformin lowers hemoglobin A1c by 1% to 2%.footnote 1
All medicines have side effects. But many people don't feel the side effects, or they are able to deal with them. Ask your pharmacist about the side effects of each medicine you take. Side effects are also listed in the information that comes with your medicine.
Here are some important things to think about:
Call 911 or other emergency services right away if you have:
Call your doctor right away if you have:
Common side effects of this medicine include:
See Drug Reference for a full list of
side effects. (Drug Reference is not available in all systems.)
When a person begins taking metformin, the dosage usually is increased
gradually to prevent side effects. You may also reduce nausea by taking the
medicine with food.
Over time, blood levels of vitamin B12 can decrease in
some people who take metformin. If you have been taking metformin for more than a few years, check with your doctor about getting a vitamin B12 test.
Lactic acidosis may occur in people who have
kidney or liver failure, have low levels of oxygen in their blood (hypoxia),
abuse alcohol, have a severe infection, or are
dehydrated. It can also result if metformin is taken
when a person has surgery or X-ray studies that use a dye. Be sure all your
doctors know that you are taking this medicine if you need a test that involves
the use of a dye or if you are having surgery. You may have to stop taking metformin temporarily.
Women who have stopped menstruating before they start
taking metformin may begin menstruating again and may become pregnant.
Medicine is one of the many tools your doctor has to treat a health problem. Taking medicine as your doctor suggests will improve your health and may prevent future problems. If you don't take your medicines properly, you may be putting your health (and perhaps your life) at risk.
There are many reasons why people have trouble taking their medicine. But in most cases, there is something you can do. For suggestions on how to work around common problems, see the topic Taking Medicines as Prescribed.
If you are pregnant, breastfeeding, or planning to get pregnant, do not use any medicines unless your doctor tells you to. Some medicines can harm your baby. This includes prescription and over-the-counter medicines, vitamins, herbs, and supplements. And make sure that all your doctors know that you are pregnant, breastfeeding, or planning to get pregnant.
Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor if you are having problems. It's also a good idea to know your test results and keep a list of the medicines you take.
Complete the new medication information form (PDF)(What is a PDF document?) to help you understand this medication.
Inzucchi SE, et al. (2012). Management of hyperglycemia in type 2 diabetes: A patient-centered approach. Diabetes Care, 35(6): 1364–1379.
ByHealthwise StaffPrimary Medical ReviewerE. Gregory Thompson, MD - Internal MedicineSpecialist Medical ReviewerDavid C.W. Lau, MD, PhD, FRCPC - Endocrinology
Current as ofMay 23, 2016
Current as of:
May 23, 2016
E. Gregory Thompson, MD - Internal Medicine & David C.W. Lau, MD, PhD, FRCPC - Endocrinology
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