Metformin: Side Effects, Dosage, Uses and More

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An increasing number of patients suffer from type II diabetes mellitus, which is a type of diabetes in which the body (liver and muscle tissue) does not absorb the excess glucose produced due to abnormal insulin resistance. For these cases metformin is usually administered.

If you are a diabetes patient or you have relatives with this condition, then keep reading this article if you want to learn about what metformin is, how to use it properly, what is the correct dosage and the possible side effects it entails, among other things.


What is Metformin?

  • Formula: C4H11N5
  • Molar mass: 129.164 g/mol
  • Half-life: 6.2 hours
  • Bioavailability: 50-60% fasting
  • Legal status: POM (UK) ℞-only (USA)
  • Excretion: Active renal excretion
  • Molar weight: 129.164 g/mol; 165.63 g/mol (hydrochloride)

Metformin is a drug belonging to a group called biguanides. This drug is an antihyperglycemic drug that is used in the first line for the treatment of type II diabetes. Indeed, it is the drug most commonly prescribed to treat diabetes.

Its scientific name is Metformin hydrochloride or Metformin hydrochloride, metformin being its active component. This drug is also known as Glucophage.

Metformin continues to help counteract the effects of diabetes mellitus. However, there are several aspects about this drug that you should be aware of for its proper use.

In what pathologies or conditions should Metformin be administered?

Metformin is used to treat type II diabetes, being administered as the only drug or together with other antidiabetic drugs such as insulin.

Being an antihyperglycemic, it promotes insulin sensitivity in the body. In this way it can regulate blood glucose levels.

In conditions such as type I diabetes, in which the patient does not produce insulin, it is useless to apply this drug, because it is not a hypoglycemic, that is, its function is not to lower blood glucose directly, but to help the body respond favorably to insulin. Therefore, this type of patient should be treated with insulin.

Although insulin can be combined with metformin (which, by itself, does not cause blood glucose lowering) to treat type II diabetes, it must be taken into account that, if this is done, there may be an increased risk of causing hypoglycemia.

What is the correct dosage of Metformin?

An important aspect is to know how to determine the correct dosage of metformin.

According to the Spanish Agency of Medicines and Health Products, the dosage and form of administration should be as follows and in the following circumstances:

  • In patients with normal renal functions, monotherapy and combination with other oral antidiabetics. The usual initial dose is of 500 mg of metformin, every 8 or 12 hours a day, or 850 mg every 24 hours, which can be administered during or after meals. This would help to avoid risks of adverse effects.

Within two weeks or less, the dosage will be adapted according to blood glucose levels. A moderate increase in dosage is recommended to avoid gastrointestinal intolerance. The maximum recommended dose of metformin is 3,000 mg per day, every 8 hours per day.

  • Under therapeutic conditions, the appropriate dose will range from 850 mg to 3,000 mg per day. Even so, this amount is already quite high, thus approaching a higher risk of causing lactic acidosis.
  • In combination with insulin, the dose of metformin to be administered will be the usual starting dose, while insulin administration will be adapted to blood sugar levels.
  • In situations of renal insufficiency, in elderly patients. In these cases, the dosage should be adjusted according to the degree of renal insufficiency of the patient. For such purposes, there should be a continuous evaluation of renal functions. Evaluation of the GFR(Glomerular Filtration Rate Test) is necessary before treating a patient using metformin. In such cases its administration should be as follows:
    • With a GFR of 60-89 ml/min, the maximum total daily dose should be 3,000 mg daily, in 2 or 3 doses.
    • With a GFR of 45-59 ml/min, the maximum total daily dose should be 2,000 mg daily, in 2 or 3 doses.
    • With a GFR of 30-44 ml/min, the total maximum daily dose should be 1,000 mg daily, in 2 or 3 doses.
  • In minor patients. It is possible to administer metformin in children aged 10-12 years. The required dose will also be the usual starting dose of 500 or 850 mg once daily, taken during or after meals. As a maximum dose, 2,000 mg per day, divided into 2 or 3 doses, is recommended.

Although several dosage proposals have been presented for a given condition, we always recommend due medical control to ensure that the dosage is correct and does not put the patient’s health at risk.

what are the uses of Metformin?

Although its main prescription is for the treatment of type II diabetes, it has been found to have other benefits in terms of metabolic, cardiovascular, neurological and other functions. It is even claimed to have anti-aging effects.

However, before giving any alternative use in the same way as other medications, you should see a doctor for an appropriate prescription according to the condition you wish to treat.

what contraindications are there regarding the consumption of Metformin?

The ones mentioned below can be included:

  • Having allergies to metformin hydrochloride or any of its excipients.
  • Having renal insufficiency with GFR values below 30 ml/min (severe renal insufficiency).
  • Suffering from any type of acute metabolic acidosis, such as lactic acidosis.
  • Having suffered from diabetic coma.
  • Suffering from hepatic insufficiency, chronic alcohol abuse problems.

For any additional information, it is essential that you consult your physician, who will provide you with further clarification.

Side effects of Metformin

Metformin can cause some side effects like any other drug. In this regard, we can mention the following:

  • Those of gastrointestinal type, such as nausea, vomiting and diarrhea.
  • Failure in the production of Folate and Vitamin B12 (consequent anemia).
  • Tendency to anorexia (lack of appetite).
  • Hepatotoxicity.
  • Lactic acidosis.


There are many aspects that can be broken down from the use of metformin, but in every situation it is advisable to consult a physician for an appropriate evaluation

The battle against diabetes is not over yet, however, with proper treatment it is possible to overcome the symptoms it causes.

Carlos José Belmonte López
Carlos José Belmonte López
Degree in Pharmacy from the University CEU San Pablo and Master's Degree from the Universidad Pontificia Comillas de Madrid. Doctorate and committed to Human Health

Aunque pueda contener afirmaciones, datos o apuntes procedentes de instituciones o profesionales sanitarios y la información contenida en PharmaSalud esté redactada por profesionales en medicina, recomendamos al lector que cualquier duda relacionada con la salud sea consultada con un profesional del ámbito sanitario.

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