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What Is metformin and what does It do?

  • Metformin is a prescription medication mainly used to treat type 2 diabetes.
  • With Type 2 diabetes, the level of sugar (glucose) in your blood is too high. Metformin lowers blood sugar to healthy levels, by improving how your body uses insulin, the hormone that controls blood sugar. It also reduces the amount of sugar your liver releases into your blood.
  • Metformin may also be used to help prevent type 2 diabetes in people at high risk of developing it (prediabetes); treat gestational diabetes (high blood sugar that develops during pregnancy); and improve fertility in women who have polycystic ovary syndrome.
  • Metformin may be sold under various brand names e.g. Glucophage, Mengen, Metored, Romidiab, Diaphage, Bigsens, Gluconorm.
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How to take metformin

  • Follow your doctor’s directions and instructions on the prescription label exactly.
  • Metformin is available as tablets, liquid or powder sachets that you dissolve in water. Don’t break up tablets.
  • It’s best to take metformin with a meal to reduce any side effects.
  • Take metformin at regular intervals. Make use of tools that assist with this such as pill organiser boxes and medication reminder apps e.g Medisafe.
  • Don’t stop taking metformin except on your doctor’s advice.
  • If you miss a dose, take that dose as soon as possible. However, if it’s almost time for your scheduled next dose, take only that dose. Don’t take double or extra doses. If you think you’ve taken too much, call your doctor or Tygerberg Poison Information Centre 24-hour number: 0861 555 777.
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What to expect when taking metformin

  • Metformin will help keep your blood sugar level stable and reduce your risk of diabetes-related problems in the future.
  • Metformin may not make you feel any different, but that doesn’t mean it’s not working, so keep taking it.
  • Metformin doesn’t cause weight gain, and may even help you lose weight. It also helps keep your cholesterol at a healthy level.
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Possible side effects of metformin

As with most medications, you may experience side effectsDon’t stop taking metformin if you have side effects; chat to your doctor first about managing these and adjusting or changing medications.

 

Common, mild side effects usually clear up within two weeks, but tell your doctor if they continue for longer or bother you.

These may include:

  • Nausea
  • Diarrhoea
  • Headache
  • Metallic taste

More serious side effects are rare, but tell your doctor immediately if you experience them.

These may include:

  • Allergic reactions – rash, itching, swelling in face, lips, tongue or throat
  • High lactic acid level – muscle pain or cramps, stomach pain, trouble breathing, tiredness.
  • Low vitamin B12 level – pain, tingling or numbness in hands or feet, muscle weakness, dizziness, confusion, difficulty concentrating.
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Safety tips for taking metformin

Some people can’t take metformin, so your doctor will check your medical history before prescribing it.

It’s especially important that your doctor knows if you have any of the following:

  • Anaemia
  • Dehydration
  • Heart disease
  • Kidney disease
  • Liver disease
  • Polycystic ovary syndrome
  • Serious infection or injury
  • Vomiting
  • A previous allergic reaction to metformin, other medications, foods, dyes or preservatives
  • You’re pregnant, trying to get pregnant, or breastfeeding.
  • Tell your doctor about all medicines (both prescription and non-prescription), herbal remedies and dietary supplements you use. Also say if you smoke, drink alcohol or use recreational drugs. Some substances may interact negatively with metformin. Others e.g. cough and cold products contain sugar or alcohol, which can affect blood sugar.
  • If you need a medical procedure such as surgery, MRI or CT scan, tell the care team you’re on metformin. You may need to stop taking it before the procedure.
  • Wear a medical ID bracelet, and carry a card that describes your condition as well as your medications and dosage times.
  • Using metformin with insulin or other diabetes drugs may increase risk of hypoglycemia (low blood sugar). Learn how to check your blood sugar, and recognise symptoms of both low and high blood sugar and how to manage them. If you have high blood sugar, or if you’re sick or exercising more than usual, your doctor might need to adjust medication doses.
  • Metformin may cause ovulation in premenopausal women who don’t have regular menstrual periods, which may increase the likelihood of becoming pregnant. Tell your doctor if you think you’re pregnant, as metformin shouldn’t be taken during pregnancy.
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Long-term metformin use: important info

  • Metformin is safe to take for a long time.
  • See your doctor for regular checkups, which may include:
  • A blood test every 3-6 months to measure your blood sugar control.
  • A kidney function test at least once a year. If your kidneys aren’t working well, your doctor may switch you to another medicine.
  • Checking the level of vitamin B12 in your blood. Metformin may reduce levels of folic acid (Vitamin B9) and vitamin B12, so make sure you get enough of these vitamins through diet and supplements.
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Where to get more help and support

 

Created and Managed by Medinformer

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National Health Service. Metformin. 2022. Available at https://www.nhs.uk/medicines/metformin/

Cleveland Clinic. Metformin Tablets. 2025. Available at https://my.clevelandclinic.org/health/drugs/20966-metformin-tablets

Diabetes South Africa. Metformin: Type 2 diabetes drug. 2020. Available at: https://www.diabetessa.org.za/metformin-type-2-diabetes-drug/