Side effects
In everyday medical practice, one speaks of “very frequent” side effects if the corresponding side effect has occurred in one in ten or at least one in a 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.
Very often nausea, vomiting, abdominal pain and diarrhea occur here. Loss of appetite may also occur. Because of this loss of appetite, metformin has also been used to treat 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.
Less than one in 10,000 test persons experienced skin reactions such as erythema (reddening of the skin) and urticaria. Urticaria, also known as hives, manifests itself in square-shaped rashes, which are very similar to those after skin contact with a stinging nettle. The rash can be accompanied by severe itching.
Scratching the skin or the wheals themselves only brings short-term relief and worsens the symptoms in the long run. Here, on the one hand, the metformin must be discontinued. On the other hand, cooling of the skin and special ointments help against itching.
In any case, a doctor should be consulted as the metformin therapy should be changed anyway. However, the incidence of these skin reactions is below 0.0001%. If 10,000 people take metformin, on average no more than one person is affected.
In very rare cases, metformin also affects the nervous system: The inhibited formation of new glucose (i.e. sugar) can lead to increased lactose production. In very rare cases, this results in so-called lactate acidosis, i.e. acidification by lactate. Very prolonged use of metformin can also, in very rare cases, result in a reduced absorption capacity of vitamin B12.
Vitamin B12, or cobalamin, is needed for cell division and blood formation and is therefore essential for the body. It can, however, be artificially substituted if necessary. Further side effects are found in the liver and bile: in very rare cases, i.e. with an incidence of 1 in 10,000, hepatitis or impaired liver function can occur.
However, this was reversible after discontinuing metformin. In any case, the liver is an extremely resistant and regenerative organ.The above mentioned metformin induced side effects have been investigated, tested and evaluated in double-blind studies with more than 10,000 participants. Overall, however, the spectrum of side effects caused by metformin is comparatively small. Lactate acidosis, however, is a very rare and dreaded complication. Further information on this is available under the heading “Complications”.
