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Metformin for Weight Loss

Supportive Care

Brand names:

Riomet®

Other names:

Glucophage, Glucophage XR

Often used for:

Weight loss, Type 2 diabetes, Polycystic ovarian syndrome (PCOS)


This information is specific to the use of metformin for weight loss. For additional information on metformin, please talk to your health care provider.

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What is metformin?

Metformin is a medicine used to control the amount of sugar (glucose) in the blood and can help patients lose extra body weight. Metformin works by lowering the amount of sugar made by the liver, lowering the amount of sugar your body absorbs from food, and helping your body use insulin better.

Metformin increases the feeling of fullness and helps people lose weight by reducing the amount of food eaten throughout the day. It works best when combined with a low-calorie diet.

The dose is slowly increased over time to limit side effects. You will have regular blood draws to check glucose levels, lactate levels, and to monitor kidney and liver function. The dose of metformin may change based on lab tests.

Brain

May be given as a tablet by mouth

 
Brain

May be given as a liquid suspension by mouth

 
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Possible side effects

  • Diarrhea 
  • Indigestion
  • Stomach pain
  • Nausea 
  • Vomiting 
  • Gas

Call your care team right away if you have symptoms of an allergic reaction. These may include: rash, hives, itching, runny nose, fever, chills, headache, muscle ache, shortness of breath, coughing, tightness in the throat, swelling of the face or neck, dizziness, low blood pressure, or pain in the chest, side, or back.  

Not all patients who take metformin will experience these side effects. Common side effects are bolded, but there may be others. Please report all suspected side effects to your doctor or pharmacist.

Find more information on side effects.

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Tips for patients and families

Be sure to discuss all questions and instructions with your health care provider or pharmacist. 

  • Metformin works best when used along with a nutrition and exercise program.
  • This medicine lowers blood sugar levels. Tell your care team if you have symptoms of low blood sugar, such as shaking, sweating, dizziness, confusion, or blurry vision.
  • Your health care provider may suggest that you take a daily multivitamin.
  • Before having a surgery or procedure with contrast, tell your care team you are taking metformin.
  • Tell your care team if you are sexually active, pregnant, or breastfeeding.
  • Sexually active patients should take steps to prevent pregnancy while taking this medicine.

Metformin at home:

  • This medicine has several dosage forms. Follow directions provided by your care team.
  • Take with food to lessen side effects.
  • Tablets: Take as directed. Swallow tablets whole. Do not crush, chew, or break before swallowing. 
  • The outer layer of the tablet may be visible in your stool.
  • Liquid: Take with the evening meal. Shake well for at least 10 seconds. Use the measuring device that comes with the medicine. 
  • In case of a missed dose, take the missed dose as soon as possible. If it is near the time for the next dose, skip the missed dose. Do not take 2 doses at the same time. 
  • Store at room temperature in a dry place. Do not store in a bathroom.

Learn more about metformin

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Always check the medication label. Many medicines look the same. Do not take any new medicine, including over-the counter medicines or supplements, without checking with your doctor or pharmacist. Talk to your doctor or pharmacist about what to do in the case of a missed dose, allergic reaction, or medical emergency. 

This information is not intended to be a complete guide and is not a substitute for talking with your provider. Medicine names, appearance, formulas, or availability may vary by clinic location. Always follow the instructions given by your care team.

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Reviewed: July 2025