Fortamet Side Effects Center

Last updated on RxList: 11/11/2020
Fortamet Side Effects Center

What Is Fortamet?

Fortamet (metformin hydrochloride) is an oral diabetes medicine for people with type 2 (non-insulin-dependent) diabetes. Metformin is sometimes used in combination with insulin or other medications, but it is not for treating type 1 diabetes. Fortamet is available in generic form.

What Are Side Effects of Fortamet?

Common side effects of Fortamet include:

  • headache,
  • muscle pain,
  • nausea,
  • vomiting,
  • stomach upset or pain,
  • diarrhea,
  • gas,
  • weakness, or
  • a metallic taste in the mouth

Fortamet does not usually cause low blood sugar (hypoglycemia). Low blood sugar may occur if Fortamet is prescribed with other anti-diabetic medications. Symptoms of low blood sugar include sudden sweating, shaking, fast heartbeat, hunger, blurred vision, dizziness, or tingling hands/feet. Tell your doctor if you experience serious side effects of Fortamet including shortness of breath, swelling or rapid weight gain, fever, body aches, or flu symptoms.

Dosage for Fortamet

Fortamet should be taken once daily. Dosage is individualized based on effectiveness and tolerance. The maximum recommended daily dose is 2500 mg. Hyperglycemia (high blood sugar) may result if you take Fortamet with drugs that raise blood sugar, such as: isoniazid, diuretics (water pills), steroids, phenothiazines, thyroid medicine, birth control pills and other hormones, seizure medicines, and diet pills, or medicines to treat asthma, colds or allergies. Hypoglycemia (low blood sugar) may result if you take Fortamet with drugs that lower blood sugar, such as: alcohol, non-steroidal anti-inflammatory drugs (NSAIDs), aspirin or other salicylates, sulfa drugs, monoamine oxidase inhibitors (MAOIs), beta-blockers, or probenecid.

What Drugs, Substances, or Supplements Interact with Fortamet?

Fortamet may also interact with furosemide, nifedipine, cimetidine or ranitidine, amiloride or triamterene, digoxin, morphine, procainamide, quinidine, trimethoprim, or vancomycin.

Fortamet During Pregnancy and Breastfeeding

During pregnancy, Fortamet should be used only when prescribed. Your doctor may direct you to use insulin instead of this product during your pregnancy. This medication can cause changes in the menstrual cycle (promote ovulation) and increase the risk of becoming pregnant. Consult your doctor about the use of reliable birth control. This medication passes into breast milk in small amounts. Consult your doctor before breast-feeding.

Additional Information

Our Fortamet (metformin hydrochloride) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


Type 2 Diabetes: Signs, Symptoms, Treatments See Slideshow
Fortamet Consumer Information

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Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Some people using metformin develop lactic acidosis, which can be fatal. Get emergency medical help if you have even mild symptoms such as:

  • unusual muscle pain;
  • feeling cold;
  • trouble breathing;
  • feeling dizzy, light-headed, tired, or very weak;
  • stomach pain, vomiting; or
  • slow or irregular heart rate.

Common side effects may include:

  • low blood sugar;
  • nausea, upset stomach; or
  • diarrhea.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


______________ is another term for type 2 diabetes. See Answer
Fortamet Professional Information


The following adverse reactions are also discussed elsewhere in the labeling:

Clinical Studies Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

In placebo-controlled trials, 781 patients were administered metformin HCl extended-release tablets. Adverse reactions reported in greater than 5% of the patients treated with metformin HCl extended-release tablets and that were more common than in placebo-treated patients are listed in Table 1.

Table 1: Adverse Reactions from Clinical Trials of Metformin HCl Extended-Release Tablets Occurring >5% and More Common than Placebo in Patients with Type 2 Diabetes Mellitus

Adverse Reaction Metformin HCl Extended-Release Tablets
Diarrhea 10% 3%
Nausea/Vomiting 7% 2%

Diarrhea led to the discontinuation of metformin HCl extended-release tablets in 0.6% of patients. Additionally, the following adverse reactions were reported in 1.0% to 5.0% of patients treated with metformin HCl extended-release tablets and were more commonly reported than in placebo-treated patients: abdominal pain, constipation, abdomen distention, dyspepsia/heartburn, flatulence, dizziness, headache, upper respiratory infection, taste disturbance.

Laboratory Tests

Vitamin B12 Concentrations

In clinical trials of 29-week duration with metformin HCl tablets, a decrease to subnormal levels of previously normal serum vitamin B12 levels was observed in approximately 7% of patients.

Postmarketing Experience

The following adverse reactions have been identified during post approval use of metformin. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

Cholestatic, hepatocellular, and mixed hepatocellular liver injury have been reported with postmarketing use of metformin.

Read the entire FDA prescribing information for Fortamet (Metformin Hcl)

© Fortamet Patient Information is supplied by Cerner Multum, Inc. and Fortamet Consumer information is supplied by First Databank, Inc., used under license and subject to their respective copyrights.

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