Metformin

Metformin is the generic name for Glucophage. Both names will be used interchangeably on this page. This medication was approved by the FDA in 2000. Glucophage is oral diabetes medication that belongs to the group of medications called the biguanides.

It works by decreasing the amount of glucose the liver releases from the glycogen storage and also decreases the amount of sugar absorbed from meals and increases the sensitivity of the body to insulin.

Glucophage is different from other diabetes medications like sulfonylureas, because Glucophage does not cause hypoglycemia and does not cause the insulin secretion by the pancreas to increase.

Also, it has been found that Glucophage does not cause weight gain, unlike other oral diabetes medications. Some patients taking Glucophage have been found to lose weight. This does not mean that people should use this diabetes medication for weight loss alone. Metformin weight loss should be an added advantage for those with type 2 diabetes who are obese.

Metformin Use

Glucophage is used to treat type 2 diabetes in adults and children over 10 years of age. It comes in different dosage strength tablets of 500mg, 850mg and 1000mg for the immediate release tablets. It is available in extended release form called Glucophage XR and comes in tablet strengths of 500mg and 750mg tablets. The diabetic person taking Glucophage is expected to adhere to diabetic diet and exercise regimen. Glucophage XR is for use in adults alone.

Glucophage does not cause hypoglycemia because it does not increase the insulin release. Hypoglycemia can occur when Glucophage is combined with other blood glucose lowering drugs, including insulin. Hypoglycemia can also occur with Glucophage and alcohol use.

Metformin Side Effects


  • Diarrhea
  • Nausea/Vomiting
  • Flatulence
  • Body weakness
  • Indigestion
  • Headache
  • Abdominal discomfort


Drug Interactions of Metformin

Steroids like prednisone and other medications that raise blood sugar, will seem to reduce the effect of Glucophage because of the increase in blood sugar that occurs.

Furosemide increases the amount of Glucophage in the blood. The clearance of the drug by the kidney may not increase and this could lead to accumulation of the medication in the blood, which by itself could raise the risk for lactic acidosis.

Nifedipine increases the amount of Glucophage absorbed into the blood and also increases the amount of the Glucohage removed by the kidney.

Metformin is an acidic drug. As such, when taken with other acidic medications, the clearance of the drug by the kidney is reduced. This is because other acidic medications are also removed by the kidney and they compete with it for clearance. This could lead to the accumulation of the medicine in the blood which increases the risk for lactic acidosis. Examples of acidic medications are digoxin, aspirin, vancomycin, Penicillins, ranitidine, morphine, Dilantin, and others.

People taking Glucophage should avoid alcohol because alcohol increases the ability of this drug to form lactic acid. This increases the chance for lactic acidosis. Also, when alcohol damages the liver, the clearance of lactate is reduced and the chance of developing lactic acidosis also increases.

Metformin Adverse Reactions


  • Glucophage causes allergic reactions to those sensitive to the medication.
  • Lactic acidosis
  • Glucophage may decrease the vitamin B12 levels in body. If a person taking Glucophage is suspected of having megaloblastic anemia, which is a rare adverse reaction of the drug, vitamin B12 deficiency should be ruled out first

Metformin and Lactic Acidosis

Lactic acidosis is a life-threatening condition that occurs due to accumulation of lactic acid in the body.

Metformin causes a rare adverse effect called lactic acidosis. Glucophage has a boxed warning for lactic acidosis. Lactic acidosis happens because Glucophage is a slightly acidic medicine that is removed by the kidney. Glucophage does not undergo change in the body, but gets removed the same way it enters the body. Glucophage is removed by the kidney and when there is problem with the kidney, liver or in heart failure, more of the medication remains in the body and cause lactic acid to accumulate. This is lactic acidosis. Lactic acid is made in the muscle when the muscle breaks down glucose without enough oxygen.

Signs and Symptoms of Lactic Acidosis are:

  • Trouble breathing.
  • Stomach ache
  • nausea
  • Vomiting
  • Muscle pain
  • Light headedness
  • Malaise
  • Weakness
  • Hypotension
  • Chills with decreased temperature

If you are taking Glucophage for sometime without problems and start to experience the above symptoms, without a known infection, you need to inform your doctor immediately. Lactic acidosis is emergency medical situation and needs to be presented to an emergency room and treated in the hospital. Most of the time hemodialysis is used to remove the excess of the drug from the blood in order to resolve lactic acidosis.

Contraindications for Metformin

The following are people who should not take Glucophage:

  • People whose kidney function is decreased or who are in kidney failure.
  • People who are allergic to the drug.
  • People who have metablolic acidosis, diabetic ketoacidosis or any acidotic condition. Glucophage should not be given to a patient in lactic acidosis.
  • People who have problem with the liver should not take this drug because it is the liver that clears the lactate that forms in the presence of this medication.
  • People who are over 80 years of age and who had not been taking this diabetic medicine should not begin treatment with Glucophage unless their doctor determines that their kidney, heart and liver are in excellent condition.
  • Patients who are receiving radiological contrast materials for laboratory test should have Glucophage stopped about two days before and after the test. This allows their kidney to clear the drug before the contrast is introduced. The contrast material needs to be cleared before Glucophage is reintroduced. Contrast material competes with Glucophage for elimination in the kidney and that can lead to accumulation of the drug in the body and cause lactic acidosis.
  • Patients undergoing surgery should not be given Glucophage. It can be restarted after surgery when the person is eating again and kidney function is determined to be normal.
  • Glucophage should also be withheld if someone has severe dehydration, shock, decreased oxygen in blood called hypoxemia or during any infection that reduces compromises the ability of the kidney to clear the drug from the blood.
  • Those in secondary failure. Secondary failure is when the medication stops being effective in a patient who had effectively used the medication for some time.
  • Stress and illness could decrease the effectiveness of Glucophage. In those instances, insulin therapy should be used until the underlying stress is resolved.
  • Pregnant and nursing mothers should not take Glucophage. Children under the age of ten years of age should also not take it. This is because the safety of the medication in those instances has not been adequately studied.

Lab Tests for Patients on Metformin


Kidney function should be checked about twice a year. This is because it is the kidney that eliminates the drug from the body. Accumulation of this medication in the kidney can damage the kidney. Only patients with normal kidney function can be given Glucophage. If the patient is over 80years of age and receiving this medicine, the dose should be the lowest effective dose and kidney function should be checked more often. If patient develops problems with the kidney, metformin should be stopped.

HA1C tests should be done periodically to determine the continued effectiveness of metformin.

Patients should also have the level of vitamin B12 done periodically, to ensure that vitamin B12 is not being lowered by the medication


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