Metformin Side Effects

by on January 23, 2012


Common metformin side effects include gastrointestinal problems such as nausea, vomiting, cramps and diarrhea. Hypoglycemia and lactic acid build-up are other more serious—but more rare—side effects of metformin. Some women may also experience vitamin B12 deficiency, and children specifically may possibly experience abnormal taste bud function and appetite loss.

Common Metformin Side Effects

The most common side effects of metformin are gastrointestinal, and include the following:

  • Nausea
  • Vomiting
  • Diarrhea
  • Cramps

Other common side effects are represented by abnormal stools, muscle pain, changes in taste sensations and occasionally difficulties in breathing.

Some patients may experience side effects in the shape of dizziness, light-headedness or flu-like symptoms, while others may have nail problems, palpitations, flushing of the face or an increase in thirst and/ or sweating.

Serious Metformin Side Effects

metformin Occasionally, patients may experience side effects of a more serious nature. These side effects include allergic reactions, which may be manifested through

  • unexplained swellings
  • hives
  • rashes
  • itching
  • wheezing and / or severe breathing difficulties.

In some cases, the Metformin may cause a disturbance in electrolytes, causing the body to function within an acidic environment, a condition known as lactic acidosis. Often occurring severely and suddenly, lactic acidosis is the result of increased levels of lactic acid, in particular when Metformin is used to inhibit the process of glucose production, hepatic gluconeogenesis.  This condition is sometimes the result of a metformin overdose and can cause severe muscle soreness.

Another more serious side effect of metformin is hypoglycemia, or low blood sugar. This occurs in individuals whose bodies are particularly sensitive to the drug; as a result, their blood sugar levels dip below the normal level.

The lactate intake of the liver may also be reduced; this is mainly experienced by individuals with kidney problems or other renal malfunctions. In rare cases, it is possible for Metformin to impair or, in extreme cases, even stop liver and kidney functions. This, however, is typically the result of an overdose. Other possibly serious side effects include deficiency of vitamin B12 and the reduction of certain hormones in a patient's blood. An overdose of the medication may, for instance, cause the level of thyroid stimulating hormones to drop significantly, especially in a person with a history of hypothyroidism.

Metformin Side Effects in Men

Side effects in men generally echo the list of common side effects, although men tend to be more susceptible to the development of hypoglycemia. This may result in episodes of dizziness, fainting and headaches, as well as being responsible for muscle pain and general fatigue. These symptoms should be reported to the patient's physician, who will then decide whether the medication should continue or not. More serious side effects sometimes occurring in men are reduction of luteinizing hormones and/ or testosterone levels in the blood.

Low testosterone levels as a result of Metformin may be indicated by a decrease in sex drive, poor performance and infertility, as well as hot flushes, an inability to concentrate, increased irritability or depression. Prolonged or severe reduction of testosterone may induce hair loss, reduced muscle mass and brittle bones. In younger men, a lack of testosterone may inhibit the production of facial and/ or body hair, slow down the development of genitalia and prevent the voice from deepening.

The occurrence of such symptoms should be investigated through a series of blood tests and may require the medication to be stopped, as well as hormone replacement therapy.

Metformin in Women & Pregnancy

While the majority of common side effects is shared by men and women, the vitamin B12 deficiency is more specific to women. Unless ignored for prolonged periods, it should not cause any serious health problems, and can be easily counteracted with a daily dose of supplements.

Side effects during pregnancy have not been fully determined as yet, resulting in the drug typically being avoided altogether during pregnancy. When used as a treatment for polycystic ovary syndrome, or PCOS, the use of the drug is usually discontinued as soon as a pregnancy is confirmed, regardless of whether it is used as a first line treatment or women with clomiphene resistance.

There is, however, no evidence of any human fetal teratogenicity with the use of the drug. Metformin has been used to effectively treat NIDDM, or non-insulin-dependent diabetes mellitus, in women without any increases in major congenital anomalies occurring. C

Metformin Side Effects in Children

Children may experience the same side effects as men and women. They have also been known to develop hypoglycemia, showing itself through sweating, unnecessary anger, shaking or disorientation, as well as occasionally producing signs of irrational anger. The drug should not be used in children below the age of 10, in people suffering from liver or kidney problems or individuals requiring dye injections for CT scans or x-rays.

Children who use metformin may also experience a few unique side effects as well, such as decrease in appetite and a bad taste in their mouths. In rare cases, typically among those with pre-existing liver or kidney conditions, a spike in blood acidity levels is also possible.

Positive Side Effects of Metformin

The first of the positive side effects is obviously represented by the weight loss triggered by this drug. Because Type 2 diabetes is more often than not accompanied by excessive weight gain, patients often have to struggle tremendously to lose this extra weight. This effort is made easier by the medication's insulin and sugar regulating action, as well as the induced lack of appetite. Naturally, this effect can be counteracted if the patient will insist on eating foods which will increase glucose levels in the blood. The rapid increase of glucose the intake of such foods generates forces the body into increased insulin production, thereby inhibiting the effect of the medication.

A few small studies have indicated that women who have used metformin consistently for over five years may develop a lower risk of breast cancer than women who take other antidiabetic drugs.  However, this has not been proven true across the board, as the studies examined only a small number of women, who may have been exhibiting special cases.

The reduction of LDL cholesterol mentioned above can also be regarded as one of the positive side effects.

Metformin - Weight Loss or Gain

There are no reported cases of weight gain, but weight loss is one of the more commonly experienced side effects. This is partly due to the fact that the drug can cause a loss of appetite. The drug's capability of regulating insulin and sugar levels within the body is also known to trigger long term weight loss. As weight gain is one of the symptoms of Type 2 diabetes, this is generally regarded as a positive effect. Studies indicate that this drug may be used as an effective treatment to achieve weight loss in obese patients, regardless of whether they are diabetic or not, although further research is required before this is to be seriously considered as a viable option.

Dealing with Worries about Side Effects

In spite of this rather long list of side effects, Metformin is regarded as safe by the FDA and continues to be a leading, widely used and very effective anti-diabetic drug. Physicians generally recommend this as a reliable anti-diabetic treatment, and patients worried about side effects should consult their doctor to discuss the matter. Any patient experiencing side effects - especially some of the more serious effects, like breathing difficulties, swelling or fainting - should consult their doctor immediately and have the situation assessed professionally.

Metformin is not safe to use in a few specific situations, such as in children under 10, in those with existing kidney or liver problems, and in individuals who need to have dye injections for x-rays and CT scans.  Only a physician is able to determine whether it will be necessary to stop the drug altogether, or whether the symptoms of side effects can be dealt with through supplements or other forms of additional treatment. It is important not to reduce dosages or stop taking the medication without seeking professional advice first.