Metformin for Type II Diabetes

Metformin is an oral antidiabetic drug indicated for the treatment of type II diabetes mellitus. It can be administered alone or in combination with other medications. We'll tell you what it is, how it works, and everything you should take into account before starting treatment with metformin.
Metformin for Type II Diabetes

Last update: 04 April, 2023

Metformin is one of the drugs available to help treat type II diabetes mellitus and help patients lead a practically normal life.

There are two types of diabetes mellitus: type I and type II. The treatment for patients with type I diabetes mellitus is insulin. In the case of type II diabetics, there’s a wide range of treatment, called non-insulin-dependent treatment.

The first step in the treatment of type II diabetes is a diet according to the patient’s needs, low in sugars or carbohydrates and combined with healthy lifestyle habits such as sports. When these recommendations aren’t enough, it’s necessary to resort to pharmacological treatment.

What is metformin and how does it work?

diabetes glycemia glucose blood

Metformin is an oral antidiabetic drug, classified within the group of biguanides. Its effect is antihyperglycemic, which means that it reduces blood sugar levels. However, it doesn’t stimulate the production of insulin, and that’s why it won’t produce hypoglycemia in the patient.

Its effect is due to three mechanisms of action:

  1. It decreases the formation of glucose in the liver, thanks to the inhibition of two metabolic pathways called gluconeogenesis and glycogenolysis.
  2. It increases muscle sensitivity to insulin, thus improving the uptake and use of blood sugar.
  3. It slows down the absorption of glucose that we ingest in our diet, maintaining a more stable level of blood sugar.

As we have commented, metformin is a drug recommended for the treatment of type II diabetes mellitus. In addition, it’s especially recommended in patients who are overweight when exercise and diet aren’t enough to control blood sugar levels.

Metformin is recommended as monotherapy (as the only treatment), but, when necessary, it can be combined with other oral antidiabetic drugs or even with insulin. In addition, it’s recommended for both adults and children over 10 years of age.

How should I take metformin?


Whether it’s prescribed as monotherapy or in combination, the recommended starting dose varies between 500 mg and 850 mg, two or three times a day, taken after meals.

Depending on the level of glucose in the blood, the dose should be adjusted after approximately two weeks. The maximum recommended dose is 3 g of metformin per day, divided into three doses.

They’re coated tablets that are administered orally. These tablets shouldn’t be chewed, but should be swallowed directly with a glass of water. It’s recommended to take them during or after meals, to avoid gastrointestinal discomfort.

If you take a single dose a day, it’s recommended to take it in the morning with your breakfast. If the doctor has prescribed two daily intakes, it’s recommended that you take them in the morning (at breakfast) and in the evening (with your dinner).

If you need to take metformin three times a day, it’s recommended to administer it during the main meals (breakfast, lunch and dinner).

In the pharmacy, you will find different presentations of metformin. There are 850 mg and 1000 mg packages. In addition, there are presentations of metformin combined with another oral antidiabetic, when it’s necessary to take both.

What should I keep in mind before taking metformin?


Metformin is contraindicated in the following cases:

  • If you have an allergy to metformin or any of its excipients
  • If you have kidney or liver problems, such as kidney failure
  • If you have very uncontrolled diabetes, severe hyperglycemia (very high blood sugar), or gastrointestinal problems, such as lactic acidosis or ketoacidosis.
  • If you suffer from alcoholism or suffer from alcohol intoxication
  • If you have any chronic heart or respiratory disease, including heart attacks
  • Acute situations of dehydration, serious infections, or shock.

Other warnings or precautions

  • Pregnancy: Poorly controlled diabetes during pregnancy can increase the risk of the fetus. There’s no evidence that the use of metformin in pregnant women can increase the risk to the fetus. Still, diabetes during pregnancy is recommended to treat with insulin.
  • Lactation: The use of metformin is not recommended if you are breastfeeding.
  • Metformin doesn’t cause hypoglycemia and therefore has no negative effects on driving. This could be different if you take metformin in combination with other oral antidiabetics.
  • Interaction with other drugs: Special care should be taken if you take other drugs, such as glucocorticoids, sympathomimetic, or diuretics.

Adverse reactions

A man vomiting.

Like all medicines, it can lead to adverse reactions during its administration. Especially at the beginning, gastrointestinal complaints such as nausea, vomiting, diarrhea, abdominal pain or weight loss may appear.

They usually disappear spontaneously after a few days. That’s why it’s recommended to take the medicine with meals or just after them and thus minimize these side effects. In addition, it’s possible that your sense of taste could be altered during treatment.

Other possible adverse reactions, but much less frequent are:

  • Lactic acidosis: Although it’s a rare complication, it’s very serious and needs immediate treatment. The risk of onset increases with uncontrolled diabetes, serious infections, prolonged fasting, dehydration, or alcohol intake, among others.
  • Reduction of vitamin B12 levels, which is significant for patients suffering from megaloblastic anemia.
  • Alterations in liver function or hepatitis, that disappear when the drug is withdrawn.
  • Skin reactions, such as skin redness or itching.


A child with tablets.

This medicine should be kept out of the reach or sight of children.

Remember that medication shouldn’t be thrown away directly and never down the drain. When you want to throw away a medicine because it has expired or you no longer need it, you should look for unwanted medication deposit points in your country.

  • Castro-Martínez MG, Castillo-Anaya V, Ochoa-Aguilar A, Godínez-Gutiérrez SA. La metformina y sus aplicaciones actuales en la clínica. Med Interna Mex. 2014;30(5):562–74.
  • Agencia Española del Medicamento y Productos Sanitarios (AEMPS). Ficha ténica, Metformina. 2014;5.
  • Luisa Estela Gil-Velázquez, María Juana Sil-Acosta, Elia R. Domínguez-Sánchez, Laura del Pilar Torres-Arreola JHM-C. Guía de práctica clínica Diagnóstico y tratamiento de la diabetes mellitus tipo 2. Abanico Vet. 2017;7(1).

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