Metformin (medicine): uses, side effects and information

Diabetes is the ninth leading cause of death in the world and is currently untreated. It is estimated that currently 1 in 11 adults worldwide have diabetes, a number that will reach 590 million people by 2035. Of all, more than 85% have type 2 diabetes.

Metformin is the most prescribed drug to treat type 2 diabetes, Which occurs because the body does not produce enough insulin and / or has developed a tolerance to the effect of insulin, due to constant exposure to high levels of it.

In this article, we will discuss what metformin is, how and for what it is used, as well as its possible side effects from its consumption.

What is metformin?

Metformin is an anti-diabetic medicine used to lower blood sugar. It belongs to the biguanide family, medicines derived from the Galician plant, its anti-glycemic properties have been known since the beginning of the 20th century.

Despite the usefulness of biguanides, its use as a diabetes medicine was initially in the background due to the commercialization of insulin. It was introduced in France in 1957 and was approved for medical use in the United States in 1995. It is currently the most widely used drug in the treatment of type 2 diabetes.

How it works?

Metformin lowers blood sugar. Although the exact mechanism of action of metformin is not yet clear, we do know that this hypoglycemic effect occurs by:

  • Decreased hepatic glucose release
  • Improved absorption of glucose by muscle cells
  • Improved absorption of glucose in erythrocytes
  • Inhibition of intestinal glucose absorption
  • Changes in the gut microbiota

These mechanisms lead to a marked decrease in hyperglycemia levels in patients taking them.Without increasing the production of insulin or increasing the weight of the patients who take it, the latter being a common effect of other medicines used to treat diabetes.


Currently, as we have mentioned, metformin is particularly useful in treating type 2 diabetes. However, there are medical professionals who prescribe it to combat obesity in patients, whether they are diabetics or no. This use of metformin is controversial, due to the side effects that this drug can generate.

Its consumption is oral, to be taken with meals to minimize side effects such as:

  • nausea
  • vomiting
  • abdominal pain
  • flatulence
  • diarrhea

Daily doses of metformin greater than 2 g should be avoided. At the start of treatment, it is recommended to start with the lowest possible dose and gradually increase it according to the patient’s needs.

Side effects

The side effects of metformin are diverse, some of them very serious although of rare incidence. Grouped according to their rarity, they would be:

1. Very common side effects

We would find the side effects mentioned above that diminish as our body gets used to the treatment. and we took the daily dose at the same time as the meals. Again, it would be vomiting, nausea, diarrhea, loss of appetite, and abdominal pain.

2. Common side effects

One in ten people taking metformin will experience changes in their sense of taste while taking it.

3. Uncommon side effects

It is estimated that one in 10,000 people taking metformin may have liver failure.The main visible symptom is the yellowing of the skin and / or eyes. Also in this range, one would find rashes on the skin, with redness or itching.

Rare but serious side effects include lactic acidosis – an increase in lactic acid in the blood which is potentially fatal if left untreated – as well as a drastic decrease in vitamin B12 levels, which is necessary for proper functioning. of the nervous system.

The main initial symptoms of lactic acidosis are nonspecific, but are usually unexplained muscle fatigue and weakness, as well as severe cramps. People with kidney disease, who are not recommended to use metformin because of the inherent risk of lactic acidosis, are at particular risk for lactic acidosis.

On the other hand, a decrease in vitamin B12 levels causes a multitude of symptoms if this deficiency is severe. One would find cases of depression, personality disorders, memory problems, gastrointestinal problems, muscle weakness and vision loss.

Also, while this has not yet been conclusively shown and more research is needed to confirm or deny this fact, the ability of metformin to increase the risk of heart attack in the people it takes.


Metformin is not indicated in people with severe liver or kidney problems. or diseases related to reduced oxygen supply, for example heart disease. On the other hand, dehydration and drinking large amounts of alcohol can increase the risk of lactic acidosis.

Although metformin does not cause hypoglycemia on its own, if it is taken in combination with other medicines to treat diabetes, we run the risk of developing hypoglycemia, which is too low blood sugar. Hypoglycemia is manifested by weakness, dizziness, sweating, increased heart rate, and impaired vision and concentration.

If you have symptoms of low blood sugar, eating sugary foods may provide temporary relief.

Metformin should also be stopped if we are going to have major surgeries or diagnostic tests with contrasts containing iodine.

Bibliographical references:

  • Forouhi, NG and Wareham, NJ (2014). Epidemiology of diabetes. Medicine (Abingdon, England: UK ed.), 42 (12), 698-702.
  • Joanna Mitri and Osama Hamdy (2009) Medicines for Diabetes and Body Weight, Expert Opinion on Drug Safety, 8: 5, 573-584.
  • Zheng, Ley (2017) “Global Etiology and Epidemiology of Type 2 Diabetes Mellitus and Its Complications”. Nature examines endocrinology.

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