What is Metformin ER: Uses, Warnings & Interactions

How to take Metformin ER

• Follow all the prescriber’s instructions. Your dose may need to be changed several times to find the most effective dose.

• Please read the medication guide and follow the patient instructions that come with this medicine. 

• Take the tablets in the evening with food or milk.

• Swallow the tablets whole. Do not crush, break, cut, or chew them.

• Store extended-release metformin at room temperature.

What to do if you miss a dose of Metformin ER

• Metformin ER tablets should only be taken in the evening.

• Skip missed doses.

• Take the next dose at its regular time in the evening.

• Do not take extra medicine to make up for a missed dose.

Metformin ER contraindications

• This medicine is not right for everyone. 

• Do not take metformin if you have:

  • Severe kidney disease

  • Chronic high acid levels in the blood (metabolic acidosis or diabetic ketoacidosis)

  • Known allergies to metformin

Metformin ER warnings

• Tell any doctor or other healthcare provider who treats you that you are taking metformin.

  • You may need to stop using this medicine before you have surgery, an X-ray, a CT scan, or other medical test.

• The prescriber needs regular blood and lab tests to check blood sugar, kidney function, and other effects of this medicine. Keep all appointments.

• Before starting metformin, tell the healthcare provider if you are pregnant, breastfeeding, drink alcohol, or have: 

  • A history of diabetic ketoacidosis or metabolic acidosis

  • Kidney disease

  • Liver disease

  • Heart problems, including heart failure

  • Vitamin B12 deficiency

  • Anemia

  • Hormone disorders

• Metformin can cause a serious condition called lactic acidosis. The prescriber will explain the symptoms and warning signs. Risk factors for developing lactic acidosis while taking metformin include:

  • Advanced age

  • Kidney or liver problems

  • Low oxygen levels (such as after a heart attack)

  • Dehydration

  • Excessive use of alcohol

  • Use of certain types of drugs

  • Surgery or medical scans using contrast dye

• This medicine can increase the risk of pregnancy in women who do not have regular periods. Metformin can cause ovulation in these women. Birth control may need to be used.

• The doctor may advise a vitamin B12 supplement while taking this medicine.

• Part of the extended-release tablet may pass in your stool as a soft mass. It may look like the original tablet. This is normal.

Metformin ER interactions

• To avoid possible drug interactions, tell the prescribing healthcare provider about all prescription drugs, over-the-counter medicines, and supplements you are using before taking this drug, particularly:

  • Insulin

  • Diabetes drugs that increase insulin levels

  • Drugs that make you urinate (diuretics)

  • Corticosteroids

  • Estrogens (either birth control pills or hormone replacement therapy)

  • Thyroid hormones

  • Blood pressure drugs called calcium channel blockers

  • Drugs called phenothiazines (usually used to treat psychosis)

  • Acetazolamide, dichlorphenamide, dolutegravir, isoniazid, phenytoin, nicotinic acid, topiramate, or zonisamide

• Alcohol should not be used excessively with metformin. Talk to the doctor about when and how much you can drink.

Find more information about metformin interactions to avoid here.