Metformin in Spain: What It Is For and What It Is Not

Metformin is the first tablet most people with type 2 diabetes are given. It lowers blood sugar by helping the body use its own insulin better. In Spain it is sold as generic metformina and under the brand Dianben, always with a prescription. It is not a weight-loss pill, although some people lose a little weight on it.

What is metformin used for?

• Type 2 diabetes. The main use. It lowers blood sugar and HbA1c, does not cause low blood sugar on its own, and does not make you gain weight.
• Prediabetes and insulin resistance. Lifestyle change comes first. A doctor may add metformin in some people at high risk, for example with a high HbA1c, obesity, or a history of gestational diabetes.
• Polycystic ovary syndrome (PCOS). It can improve insulin resistance and, in some women, the regularity of periods. This use is off-label in Spain: the doctor decides case by case and explains why.
• Gestational diabetes, in some cases, under specialist care.

What is metformin called in Spain?

Most boxes say metformina followed by the maker's name. The historic Spanish brand is Dianben. If your tablets at home are Glucophage, Glumetza or Fortamet, the medicine is the same. Metformin also comes combined with other diabetes drugs in one tablet, under brand names such as Janumet or Eucreas. Bring the box or a photo of it to any appointment: the combination matters.

There are standard tablets and slow-release tablets (liberación prolongada). The slow-release form is often gentler on the stomach. Your doctor chooses the form; do not swap between them on your own.

Is metformin a weight-loss pill?

No. Metformin is not approved for weight loss, and it is not a slimming drug. Some people lose a small amount of weight, mainly because it reduces appetite a little and does not add weight the way some other diabetes tablets do. That effect is modest and not the reason to take it. If weight is the problem, the options are reviewed on our weight optimization page, and a doctor explains which treatments are approved for that purpose.

Do you need a prescription for metformin in Spain?

Yes. Metformin is prescription-only in Spain. Pharmacies cannot sell it without one, whatever the box you show from another country. A doctor in Spain can review your diagnosis, your latest results and your current treatment by video and, if it is appropriate, issue a private electronic prescription that any Spanish pharmacy accepts. Our type 2 diabetes page explains what that review covers.

What are the side effects?

The most common are stomach effects: nausea, loose stools, wind, belly discomfort and a metallic taste. They usually appear in the first weeks and settle. Taking the tablets with meals, as the leaflet says, helps. If they do not settle, tell your doctor: a slow-release tablet or a different plan may suit you better.

Two rarer points matter more:

• Vitamin B12. Long-term metformin lowers B12 in some people, which can cause tiredness, numb or tingling feet and anaemia. B12 is checked every so often, and more often if you have symptoms.
• Lactic acidosis. A very rare but serious build-up of acid in the blood. The risk rises when the kidneys are not working well, with heavy alcohol use, and during severe dehydration or serious illness. That is why kidney function is tested before and during treatment.

Which blood tests go with metformin?

• HbA1c, to see how well sugar is controlled over the last three months. Read our guide on HbA1c and prediabetes results.
• Kidney function (creatinine and eGFR), before starting and at least once a year, more often if it is reduced. Metformin is adjusted or stopped if the kidneys weaken.
• Vitamin B12, from time to time during long-term use.

When might metformin be paused?

Your doctor may tell you to stop it for a short time around a scan with iodine contrast, an operation, or an illness with vomiting, diarrhoea or fever that leaves you dehydrated. Restart only when the doctor says so. Do not stop it on your own because your sugar "looks fine": high sugar often has no symptoms.

Can you drink alcohol on metformin?

Small amounts with food are usually fine. Heavy or binge drinking raises the risk of lactic acidosis and low blood sugar. If you drink a lot, say so at the appointment; it changes the advice.

When to see a doctor

• Stomach effects that have not settled after a few weeks, or that stop you taking the tablets.
• Tiredness, numb or tingling feet, or a sore tongue, which can point to low B12.
• You have run out of tablets in Spain and have no local prescription.
• You are planning pregnancy, or you have become pregnant.

When to call 112

• Fast, deep breathing, severe belly pain, muscle cramps and feeling very cold or drowsy: possible lactic acidosis.
• Confusion or fainting, especially if you also take insulin or other diabetes tablets.

Getting a medical assessment

If you are unsure whether metformin is right for you, you can book a video consultation with Dr. Pedro Yelamo Vera, a physician registered in Spain. You can also read more about type 2 diabetes care and PCOS and insulin resistance. A prescription is never guaranteed: it is issued only where clinically appropriate after a genuine evaluation, as a private electronic prescription under Spanish law. This service is for urgent, non-emergency care. In an emergency, call 112.

Frequently asked questions

Sources

• AEMPS – CIMA: official medicine information (search "metformina")
• NHS: Metformin
• MedlinePlus: Metformin
• Mayo Clinic: Type 2 diabetes, diagnosis and treatment
• NICE NG28: Type 2 diabetes in adults, management

This guide is general information. It does not replace the package leaflet or the advice of your doctor or pharmacist.