How should I take metformin?

You should always follow your doctor’s specific instructions for taking any medication, including metformin. But there are some general rules that will probably apply to you:
  • If you don’t notice a change in your blood glucose right away, don’t stop taking your metformin. It takes about three to four weeks for metformin to reach its full effect.
  • If your symptoms go away or you decide you feel fine now, don’t stop taking metformin. You need this medication to stay well.
  • If you forget to take a dose, take it as soon as you remember. If it’s already time for your next dose, just take the usual amount. Do not double your dose.
  • If you take extended-release metformin (Glucophage XR), be sure to swallow the pill whole. Don’t chew, crush or split the pill.
  • If you don’t follow your meal plan -- you overeat, skip a meal or make a poor food choice -- don’t adjust your metformin dose.
  • If you’re sick, most of the time, you should keep taking metformin as prescribed. However, if you’re throwing up or dehydrated, stop taking your metformin. Call your doctor for additional instructions.
  • If you’re scheduled for a medical procedure, make sure that the doctor and nurses know that you take metformin. You might need to stop taking it for a short time if you have to fast beforehand or if you’re having a surgery or x-ray that uses contrast dye. Ask for instructions.
Audrey K. Chun, MD
Geriatric Medicine
Metformin (prescribed to treat type 2 diabetes) should be taken with meals. If you eat less than usual or start to exercise more, tell your doctor, as this can affect your blood sugar and your dosage may need adjusting. Limit or stop your alcohol intake if you are taking metformin. Certain drugs and supplements may interact with metformin, so make sure your doctor is aware of any other medications you take.

If you're having surgery (including dental surgery), any x-ray procedure in which dye is injected, or any major medical procedure, tell your doctor that you are taking metformin. Metformin should not be used in patients with renal impairment and should be used cautiously in patients ages 80 and older. It should be stopped if you have a severe illness that causes dehydration, low blood pressure or oxygenation, like worsening heart failure or chronic obstructive pulmonary disease (COPD), since these can increase the risk of lactic acidosis.

Metformin is taken in tablet or solution form. It comes in various dosages and is often used in combination with other medications. Your dosage will be determined by your doctor. Metformin should be used in combination with a diet and exercise program. This medication comes in a regular and extended-release form. It is usually taken with meals. Do not crush or chew tablets. You may have to take extra B12 vitamins while taking metformin. Because this drug can cause changes in your blood sugar, you need to be aware of symptoms of hypoglycemia (low blood sugar) and be prepared to take a source of sugar, such as candy or orange juice if needed. Blood glucose monitoring will be used to determine your response to metformin.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.