Metformin: Dosages, side effects & Special instructions

Metformin medicine information

Metformin is a biguanide anti-hyperglycemic agent used for treating type 2 diabetes. Metformin is an oral diabetes medicine that helps control blood sugar levels. Additionally, it is used together with diet and exercise to improve blood sugar control.

However, metformin works by decreasing the amount of glucose you absorb from your food. Also, it decreases the amount of glucose made by your liver. Moreover, it increases your body’s response to insulin and  increasing the use of sugar by your muscles.

Metformin is also used for polycystic ovarian syndrome (PCOS). This is an off-licence use. That is why so you won’t find it in the information leaflets that come with the medicine. However, it is a widely used treatment option for this condition.

Before taking this medicine

You should not use metformin if you are allergic to it. Tell your doctor if you have or ever had:

  • severe kidney disease 
  • high ketone levels in your blood or urine;
  • heart disease, congestive heart failure;
  • liver disease 
  • if you also use insulin, or other oral diabetes medications
  • you’re breastfeeding
  • if you are pregnant or pregnant whiles taking metformin

If you need to have surgery or any type of x-ray or CT scan using a dye that is injected into your veins, you will need to temporarily stop taking the medicine.

Furthermore, you may develop lactic acidosis, a dangerous build-up of lactic acid in your blood. This may be more likely if you have other medical conditions such as, a severe infection, chronic alcoholism, or if you are 65 or older. Ask your doctor about your risk.


  • The usual dose for adults with diabetes starts with 500 mg (1 tablet) 1–2 times daily. However, it gradually increases as tolerated to 1–2 g daily in divided doses.
  • Your doctor will usually start you on a low dose and increase the dose gradually. But it depends on your blood sugar level. This allows your body to get used to the medicine and also reduces adverse effects.
  • Treatment for diabetes is usually lifelong. Keep taking metformin everyday to control your diabetes. Speak to your doctor, nurse or pharmacist before stopping.

How to take metformin

  • Always take metformin with food, during a meal or just after a snack.
  • Take metformin at the same times each day.
  • Do not skip meals while taking metformin.
  • Take metformin exactly as prescribed by your doctor.
  • Follow all directions on your prescription label. Also read all medication guides or instruction sheets.
  • Your doctor may occasionally change your dose. Use the medicine exactly as directed.
  • Do not crush, chew, or break the tablet. Swallow it whole.

Special instructions

Low blood sugar (hypoglycemia) can happen to everyone who has diabetes. Symptoms include headache, hunger, sweating, irritability, dizziness, nausea, fast heart rate, and feeling anxious or shaky. To quickly treat low blood sugar, always keep a fast-acting source of sugar with you such as fruit juice, hard candy, crackers.

It is likely to occur if you delay or miss a meal or snack, drink alcohol, exercise more than usual, or cannot eat because of nausea or vomiting.

Metformin is only part of a complete treatment program. Others may also include diet, exercise, weight control, regular blood sugar testing, and special medical care. Follow your doctor’s instructions very closely.

What happens if you miss a dose

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

What if you take too much

If you take too many tablets by accident, contact your doctor or hospital straight away. An overdose of a large number of metformin tablets can cause serious health problems. The symptoms are severe and quick to appear.

If you need to go to hospital, take the packet or leaflet inside it. Also, remember to take any remaining medicine with you to the hospital.

Metformin side effects

Get emergency medical help if you have signs of an allergic reaction to metformin. Signs such as hives, difficulty in breathing, swelling of your face, lips, tongue, or throat. Get emergency medical help if you have even mild symptoms such as:

Common side effects may include:

This is not a complete list of side effects as others may occur.

Pregnancy and breastfeeding

Metformin is usually safe to take during pregnancy – either alone or in combination with insulin.

Metformin and breastfeeding

You can take metformin while you’re breastfeeding. It passes into breast milk but the amount is too small to affect your baby.

About felclinic 593 Articles
Felix Ntifo is a Registered General Nurse who has so much passion to improve health care delivery. He founded FelClinic with the hope of making health information accessible to everyone who may not come in contact with him personally. "At we are very passionate about health and well-being of everyone. Our team is made up of professional doctors, nurses, midwives and lab technicians."

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