Metformin is a prescription only medication used to manage high blood sugar levels in people who have type 2 diabetes, gestational diabetes, or sometimes for those who are at high risk of type 2 diabetes. There are two types of metformin: standard release and slow release. Metformin is also the name of the active ingredient.

Metformin is a generic medication, meaning it is available in its generic form sold as “Metformin”. There are also branded versions, such as Gluchophage, Axpinet, and Diagemet, which contain the same active ingredient: metformin. Branded medications are usually more expensive, but they work in the same way as their generic counterparts.

Metformin is also sometimes used for polycystic ovary syndrome; however, it is not officially licensed for this.

When you have type 2 diabetes the body does not produce enough insulin, or the insulin it produces is not effective. This can lead to high blood sugar levels (hyperglycaemia). Metformin works by helping your body use the hormone, insulin, more effectively and decreasing the sugar produced by your liver. If you have type 2 diabetes, your body cannot control your blood sugar levels effectively. This is because your body is not producing enough insulin or it is not responding well to the insulin produced (called insulin resistance). Insulin helps your body to use sugar as energy. When there is not enough of it or it is not being used effectively by your body, it can cause increased blood sugar levels.

As well as decreasing blood sugars produced by your liver and increasing your body’s sensitivity to insulin, Metformin decreases how much sugar your body absorbs from the food you eat.

How long does Metformin take to work?

The speed at which Metformin begins to work will vary between individuals, and will also be affected by the dosage and format you take. Some people may get reduced blood sugar levels within the first week. However, it can take several months for Metformin to have its full effect.

How do I know if Metformin is working?

Signs that indicate that Metformin appears to be working include:

• lower blood sugar levels
• lower haemoglobin A1c levels (a longer-term measure of blood sugar levels)
• some weight loss, or no weight gain

However, these signs will not necessarily be the same for everyone. Speak to your doctor if you are unsure whether or not Metformin is working.

What is the difference between Metformin standard release and Metformin modified release?

Standard release tablets release Metformin into your body quickly and are typically taken several times per day. Modified or slow release tablets work over a longer period, meaning you do not need to take them as regularly. Your doctor or pharmacist will explain which version of Metformin you are being prescribed and how you should take them. Metformin also comes in liquid and sachet form for people who cannot swallow or would have difficulty swallowing tablets.

You must take Metformin tablets according to how they were prescribed. This will ensure that the drugs are as effective as possible.

Metformin tablets are available in different strengths. Your doctor will prescribe an appropriate dosing schedule, which may change in future in accordance with test results. You will normally be asked to start on a lower dose of metformin which increases over time up to your normal dose. This can help to reduce the possibility of getting side effects.

How and when to take Metformin

Swallow Metformin tablets whole with water, do not chew them. Standard-release tablets can be crushed and added to your food, however you cannot do this with modified or slow release tablets. If you are using a sachet or liquid form, add it to a glass of water and stir until dissolved, then drink immediately.

Your doctor will provide you with a dosing schedule for Metformin. Each person’s dosing schedule is different, and you must follow the one given to you. Take Metformin just after or with your evening meal. This can help to reduce the potential for side effects.

How long do I take Metformin for?

Diabetes treatments are usually for life. However, you may have to switch from Metformin to another medication if you get other conditions such as kidney failure or if you get side effects from Metformin. Do not stop taking Metformin without speaking to your doctor about it first, as this will cause your blood sugar levels to spike and your diabetes will worsen.

What if I forget to take Metformin?

If you forget to take your metformin, skip the missed dose, take the next dose as usual, and continue with your dosing schedule. Do not take a double dose of Metformin.

What if I take too much Metformin?

If you take more metformin than you should, you may experience lactic acidosis. The symptoms of lactic acidosis include:

• being sick
• stomach ache
• muscle cramps
• generally feeling unwell
• extreme tiredness
• breathing difficulties
• fever
• raised heart rate

If you have taken too much metformin and you experience any of these symptoms, you should stop taking metformin and call 999 or go to A&E.

Metformin is available in several doses, typically between 500 milligrams (mg) and 1000mg per tablet. The specific dose you need will be decided by your doctor based on your medical condition. Examples of dosing schedules for Metformin can be found on the NHS website, however it is important you carefully follow the prescription instructions given to you.

What is the minimum and maximum dosage of Metformin?

There is no specific minimum dose of Metformin, however, it is likely your doctor will advise you to gradually increase your dose when you start taking it to reduce the possibility of side effects. The highest dose of Metformin is 2000mg per day, usually taken as four tablets of 500mg. Liquid format Metformin comes in 5ml doses which contain either 500mg, 850mg, or 1000mg of metformin. Metformin sachets are available in doses of 500mg or 1000mg.

Your doctor will monitor your blood sugar levels regularly, which may result in changes being made to your dosing schedule.

If you have a prescription you can buy Metformin from online doctors and pharmacies like Superdrug Online Doctor or at most local pharmacies.

Metformin is not available over the counter, and you should never take it unless it’s been prescribed to you.

Can I get Metformin on the NHS?

Yes, Metformin is available on the NHS. People with diabetes are entitled to free prescriptions for all of their medications including those for diabetes. Speak to your GP about getting a medical exemption certificate for your prescriptions if you have diabetes.

Like any medication, Metformin can cause side effects. However, not everyone gets side effects. It depends on the individual. Taking Metformin with a meal can reduce your chances of getting side effects.

The most common side effects of Metformin include:

• feeling sick
• being sick
• diarrhoea
• stomach-ache
• loss of appetite
• vitamin B12 deficiency (when taking high doses or for long-term use)

Other common side effects of Metformin include:

• changes in your taste

Metformin does not cause weight gain, unlike some other diabetes medications.

Very rare side effects (up to 1 in every 10,000 people taking Metformin):

• skin reactions including redness or itching
• hepatitis
• abnormalities in liver function tests
• lactic acidosis

What should I do if I get Metformin side effects?

If you get side effects, speak to your doctor, pharmacist, or nurse as soon as possible. If the side effects are as serious as suspected lactic acidosis, call an ambulance or go to A&E.

You may also wish to report any side effects you get to the Yellow Card Scheme by going to www.mhra.gov.uk/yellowcard. Reporting can help improve understanding of possible Metformin side effects.

How long do Metformin side effects last?

The type, duration, and severity of potential side effects of Metformin will depend on the individual. Most mild side effects should go away on their own as your body gets used to the medication.

Metformin may not be right for everyone. Certain conditions or certain medications can interact with it and make it less effective, or potentially unsafe. Always speak to your doctor or pharmacist about any other medications you are taking, have recently taken, or are planning to start taking before you start to take Metformin.

Avoid excessive alcohol intake with Metformin.

Medicines which may interact with Metformin

It is important to tell your doctor or pharmacist if you take any of the following medications before you start taking Metformin:

• other diabetes medication
• diuretics (drugs which increase urine production) such as salbutamol beta-2 agonist or terbutaline for asthma
• corticosteroids, such as for skin inflammation or asthma
• non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen and celecoxib
• medicines that may alter the amount of metformin in your blood; verapamil, rifampicin, cimetidine, dolutegravir, ranolazine, trimethoprim, vandetanib, isavuconazole, crizotinib, olaparib
• high blood pressure medications

Metformin with pregnancy and/or breastfeeding

Metformin may be suitable for you if you are pregnant, however you must speak to your doctor for advice first. Metformin is not suitable for those who are breastfeeding. Speak to your doctor if you wish to breastfeed but have been prescribed Metformin.

Driving and using machines

Taking Metformin in combination with other diabetes medicines can cause low blood sugar (hypoglycaemia). Symptoms include weakness, dizziness, increased sweating, rapid heart beat, vision disorders or difficulty concentrating. Do not drive if you get these symptoms, and seek immediate medical help.

Metformin is one of the most prescribed medications for type 2 diabetes. However, there are several other types of medications which can be prescribed to lower blood sugar levels. These include:

• sulfonylureas, such as gliclazide
• pioglitazone
• DPP-4 inhibitors, such as saxagliptin
• SGLT2 inhibitors, such as dapagliflozin
• GLP-1 agonists, such as exenatide
• insulin

These medicines can be prescribed individually or in combination with metformin.