Side effects of metformin


Metformin, used to treat type 2 diabetes

Metformin is one of the most popular drugs used to treat type 2 diabetes. Type 2 diabetes is an acquired type of diabetes, also known as age diabetes, which, if there is a genetic predisposition, is aggravated by obesity and leads to permanently high blood sugar levels.

To reduce the excessively high sugar level in the blood, the body has a very effective hormone, insulin. Since the pancreas - also known as the pancreas - can no longer keep up with the production of insulin and quit its job, the body can no longer lower the insulin level by itself after a certain point in time. To make matters worse, the body cells no longer react to insulin over time, i.e. insulin resistance sets in.

The combination of these two factors leads to type 2 diabetes. Metformin helps to lower blood sugar levels. It is now considered the drug of choice for the treatment of diabetes mellitus and is used in millions of cases worldwide for the treatment of type 2 diabetes mellitus.

Mechanism of action

The exact mechanism of action of metformin is not yet 100% clear. On the one hand, metformin inhibits the formation of new sugar in the body itself. This takes place primarily in the liver. On the other hand, it is discussed whether metformin also reduces sugar intake in Intestines inhibits. This would mean that sugar ingested with food would no longer reach the blood via the intestinal wall. However, whether metformin actually inhibits this process is a matter of debate.

However, some bodybuilders use metformin to lower their body's fat percentage. Because if metformin actually inhibits the absorption of sugar in the intestine, less sugar is converted into less fat - and the body fat percentage drops. The undoubtedly helpful effects of metformin can, however, be associated with various side effects and should only be taken if there is an actual indication, i.e. diabetes type 2 disease.

Side effects

In everyday medical practice, one speaks of "very frequent" side effects when the corresponding side effect occurred in one in ten to at least one in one hundred test persons. This corresponds to every tenth to every hundredth test person, or 1-10% of all patients.

A very common side effect of metformin affects the gastrointestinal tract, or digestive tract for short. Very often occur here nausea, Vomit, stomach pain, and diarrhea on. Loss of appetite can also occur. Due to this loss of appetite, metformin was also used for the therapy of overweight adolescents - unfortunately without success. The gastrointestinal side effects can be avoided by slowly increasing the dose. They also often disappear in the course of therapy.

Other side effects affect the skin. Fewer than 1 in 10,000 test persons had skin reactions such as Erythema (Reddening of the skin) and Urticaria come. Urticaria, too Hives, manifests itself in wheal-shaped rashes that are very similar to those after skin contact with a nettle. The rash can be very itchy. Scratching the skin or the wheals themselves only bring short-term relief and worsen the symptoms in the long run. On the one hand, the metformin must be discontinued here. On the other hand, it helps against that itching a cooling of the skin, as well as special ointments. In any case, a doctor should be consulted, as the metformin therapy should be changed anyway. However, the incidence of these skin reactions is less than 0.0001%. If 10,000 people take metformin, an average of one person is affected.

In very rare cases, metformin also has an effect on the nervous system: the inhibited formation of new glucose (i.e. sugar) can lead to an increased formation of lactose. In very rare cases this results in a so-called Lactic acidosis, so an overacidification by Lactate. If metformin is used for a very long time, it can also, in very rare cases, lead to a reduced absorption of Vitamin B12 come. Vitamin B12, or also Cobalamin is required for cell division and blood formation, and is therefore essential for the body. However, it can be artificially substituted if necessary.

Further side effects can be found at liver and bile: In very rare cases, with an incidence of 1 in 10,000, it can hepatitis, or impaired liver function. However, this was reversible after discontinuation of metformin. The liver is an extremely resilient and regenerable organ anyway.

The above-mentioned side effects caused by metformin have been examined, tested and evaluated in double-blind studies with more than 10,000 participants. Overall, however, the range of side effects of metformin is comparatively low. A very rare, dreaded complication, however, is the Lactic acidosis further information will follow under the heading "Complications".


When taking metformin, it can in very rare individual cases Lactic acidosis come. The reason for this is that the production of new sugar in the liver is disturbed. Instead of commercial sugar (glucose), lactate is produced. Metformin inhibits a cell transporter that brings building blocks into the cell that are needed there for glucose production. As a result, lactate is not produced there, but rather glucose. Lactate is an "acid ion" of lactic acid. Too much lactic acid - as the name suggests - leads to one Acidification of the body. This sinks the PH value of the body, and a dreaded complication occurs: lactic acidosis.

Lactic acidosis is an excess of acidity in the body caused by lactates. The body reacts very sensitively to changes in its pH value. Even the smallest fluctuations can lead to a shock and Kidney failure to lead. It is therefore particularly important to monitor kidney values ​​during metformin therapy. The kidney is responsible for the elimination of toxins in the body. It produces the urine, which contains water and waste. Lactate can also be excreted via the kidneys - but only if the kidneys have a correspondingly high excretion capacity. A impaired kidney function with a filtration rate of less than 45 ml per minute is therefore a contraindication to metformin therapy. In general, all situations that lead to over-acidification of the body should be avoided.

Next shock and Kidney failure, it can also close if the value is weak Muscle aches come. Competitive athletes are often affected by this: If at the end of the day the muscles are “over-acidic”, this means nothing other than that too much acid has accumulated in the muscles and impairs their function. The muscles then feel rock hard. This is an experience especially for inexperienced climbers who have spent an hour or two on the climbing wall. For the rest of the day there is nothing left to do with the muscles, and the next day you can expect a heavy one Muscle aches, also as "achingThis type of muscle pain can occur as a result of lactic acidosis all over the body.

Acidosis is also associated with deep, heavy breathing. For outsiders, this can give the impression of Shortness of breath awaken in the person concerned. In fact, this is called "Kussmaul breathing“Labeled breathing potentially life threatening. It is a way of the body to defend itself against the increasing acidity. The deep breathing causes more CO2 to be exhaled, which shifts the acid-base balance in the body in the direction of basic - that is, quasi "sweet". The smell of the air you breathe is typically acetone (smell is similar to the smell of nail polish remover), which can be a crucial indicator in an emergency.

Unfortunately, that's not all: There are other reasons that can lead to life-threatening lactic acidosis, such as alcohol: Excessive alcohol consumption also leads to acidification of the body. The simultaneous Use of metformin and alcohol is contraindicated.

However, alcohol consumption should also be avoided for other reasons: Alcohol contains a lot of sugar, and is very energetic. In addition to the usual side effects that can occur after many years of alcohol consumption, alcohol does not help in weight loss. The alcohol drives that Blood sugar level and causes hunger. In other words, exactly the opposite of what you actually want to achieve with metformin therapy.

Successful therapy for type 2 diabetes always includes a change in lifestyle by changing diet and exercise, especially in the case of overweight or obesity. Therefore, at best, the consumption of alcohol should be avoided completely. Of course, nothing speaks against a glass of sparkling wine for a birthday, because not every sip of alcohol leads directly to lactic acidosis. Regardless of this, alcohol consumption should be combined with a meal.

A Lactic acidosis is in principle a very rare event, and occurs in less than 1 in 10,000 cases after taking metformin. However, the risk increases with alcohol consumption, poor kidney function, and general hypersensitivity to metformin. However, as long as the therapy is carried out as prescribed by the doctor, the risk is very low.


Further effects that were shown when taking metformin and that some type 2 diabetes patients will certainly be happy about were known in studies from 2009: Metformin is suspected of significantly increasing the general cancer risk - by up to a third reduce. Further, large-scale studies with more than 100,000 test persons showed in 2011 that taking metformin led to a significantly reduced risk of rectal tumors. How metformin reduces the tumor risk is not yet known. The cause of this is to be investigated in further studies.

Further information
  • diabetes
  • Diabetes mellitus
  • Type 1 diabetes mellitus
  • Type 2 diabetes mellitus
  • Diabetes mellitus symptoms
  • Diet in Diabetes
  • Therapy diabetes
  • Drugs diabetes mellitus
  • Table of contents Diabetes mellitus
  • Metformin PCO
  • Metformin and alcohol - are they compatible?

Further subjects that might interest you:

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  • Aplphaglucosidase inhibitors
  • Amaryl
  • Glinide
  • Glucophage
  • Lantus®
  • Metformin
  • Sulfonylurea
  • insulin

All information from the field of medication can also be found under Medicines A-Z!

Exclusion of liability / disclaimer

We would like to point out that medication must never be discontinued, applied or changed independently without consulting your doctor.
Please note that we cannot claim that our texts are complete or correct. The information may be out of date due to current developments.