Metformin HCL (metformin)

Important information about metformin:

  • Metformin is a medicine that is taken by mouth to treat or prevent type 2 diabetes.

  • It is used to help keep blood sugars in range. It helps your body use the insulin that it makes in a better way. It may also help with weight loss.

  • Metformin is sometimes used with other diabetes medicine like insulin.

Metformin works to lower your blood sugar in several ways. It helps:

  • Your body use the sugar from the food you eat.

  • The liver make less sugar.

  • Your body's own insulin to work better.

Like all medicines, metformin may cause side effects. Not everyone will have side effects.

Common side effects include:

  • Diarrhea

  • Nausea

  • Vomiting

  • Bloating or gas

  • These side effects are common when you start taking metformin. Taking metformin every day allows the body to get used to the medicine and side effects should go away within the first 2 weeks.

Lactic acidosis is a rare side effect. This is dangerous. Symptoms of lactic acidosis include:

  • Weakness

  • Muscle pain

  • Trouble breathing

  • If your child has any of these symptoms, stop the metformin and call 215-590-1000 immediately and ask to speak with the Endocrine fellow on call.

Safety and monitoring:

Metformin is prescribed for children ages 10-18 years of age and for adults. Your child may not be able to take metformin if they:

  • Have liver or kidney problems

  • Have severe heart problems, such as heart failure

  • Drink alcohol

Laboratory tests may be ordered before starting metformin and during treatment.

These lab tests may include:

  • Liver function tests

  • Kidney function tests

  • HbA1c test

  • Hemoglobin and hematocrit test

Metformin and pregnancy:

  • If you are or plan to become pregnant, talk to your healthcare provider before starting metformin.

  • A pregnancy test may be ordered with your routine lab test.

  • If you are sexually active, use birth control such as condoms or hormonal birth control prevent pregnancy.

  • If you have questions about this, please discuss it with your healthcare provider.

Patient instructions for taking metformin:

  • Give metformin with or after meals.

  • Taking metformin after eating may help avoid common side effects.

Metformin comes in different forms. It is taken once or twice daily.

  • Immediate release - can be crushed to mix with food. It can also be cut to help with swallowing the pill.

  • Extended release - should NOT be crushed or cut.

  • Liquid- ask for liquid metformin if your child is not able to swallow pills.

Your child will start with small doses. It usually takes 4 weeks to get up to a full dose. A typical metformin schedule looks like this:

  • Week 1 - 1 pill with dinner

  • Week 2 - 1 pill with breakfast and 1 pill with dinner (immediate release) OR 2 pills with dinner (extended release)

  • Week 3 - 1 pill with breakfast and 2 pills with dinner (immediate release) OR 3 pills with dinner (extended release)

  • Week 4 and beyond - 2 pills with breakfast and 2 pills with dinner (immediate release) OR 4 pills with dinner (extended release)

Things to remember while taking metformin:

  • Do not take metformin on an empty stomach. Take it with food to prevent stomach upset.

  • Tell your health care provider if your child is having surgery or an X-ray procedure with dye.

  • Stop metformin 48 hours before getting an X-ray procedure or CT scan with dye or contrast. Do not re-start metformin until 24 hours after your X-ray or CT scan.

  • Stop taking metformin 24 hours before having surgery. Do not re-start metformin until you are eating and drinking normally after surgery.

  • Taking metformin alone does not cause low blood sugars.

  • Taking metformin combined with other diabetes medicines, including insulin can cause low blood sugars.

  • Remember to tell all your healthcare providers that you take metformin.

 

Reviewed July 2025 by Bob Squaresky, MS, RD, LDN, CDCES, CPT, Jessica Zook, PharmD