Metformin Side Effects: Common, Severe and Long Term

Medically Reviewed By: DR. MOHAMMAD SULEMAN, Consultant Diabetologist, MBBS January 25, 2024

Last updated on July 28th, 2023

Metformin is a very popular and commonly used oral medication for treating and managing type-2 diabetes. The objective of the treatment of type-2 diabetes is to manage blood glucose levels mainly. The body’s blood glucose levels fluctuate due to the body’s resistance to insulin and the reduction in insulin production. Metformin 500 mg thus aims to control these fluctuating blood glucose levels. Read this article to learn about the side effects of metformin medicine.

Metformin Need- Type 2 Diabetes and Liver role

The liver and pancreas help in maintaining blood glucose levels. Insulin is secreted by the pancreas when the glucose from the digestion of food enters the bloodstream. It is with the help of insulin the body cells can absorb the glucose for energy and metabolism. However, the excessive body glucose is stored in the liver as hepatic glycogen.

During emergency needs, the hepatic glycogen from the liver is broken down to release glucose. Due to diabetes, the body becomes resistant to insulin. Thus, the body cell absorption of glucose decreases. Cells need energy, and thus liver starts converting the stored hepatic glycogen into glucose. This, in turn, increases the glucose level in the bloodstream.

Thus, in type-2 diabetes, hepatic glucose production is high, resulting in high blood glucose levels. Thus, there is a need to control hepatic glucose production. According to the National Library of Medicine (NLM), metformin is an oral medicine that reduces hepatic glucose production by the liver.


Metformin is an oral medicine that reduces the hepatic glucose production of the liver. In this way, it controls blood glucose levels for type-2 diabetes management.

Read More: Vildagliptin Tablet: Uses and Side Effects

Metformin Uses: What is metformin used for?

Metformin Uses: What is metformin used for?

  • Manages Type-2 diabetes by controlling liver glucose production: According to Oxford Academic, metformin acts as an inhibitor to the respiratory chain of the liver. This inhibition results in a decrease in hepatic glucose production. Thus, metformin manages glucose production in the liver.
  • Insulin sensitivity: It also helps in increasing the insulin sensitivity of the cells. This helps in controlling the glucose levels of the body.
  • Increased glucose utilization: As per a study conducted by the NIH, metformin helps in increasing the body’s glucose utilization in the intestine. This, in turn, regulates the blood glucose levels.
  • Weight management: Metformin alters the body’s stored fat usage. It also reduces your appetite and thus is used in weight management.
  • Polycystic ovary syndrome: Metformin stimulates ovulation and thus helps treat polycystic ovary syndrome.


Metformin usages control blood glucose levels, weight management, and polycystic ovary syndrome management.

Metformin Drug Information & Dosages

It comes under different brand names namely: Glucophage, Glucophage XR, Fortamet, Glumetza, and Riomet.

Oral tablets of Metformin are also available in different doses. Immediate-release Metformin tablets are available as Metformin 500 mg, Metformin 850 mg, and Metformin 1000mg. Extended-release tablets are available as Metformin 500 mg, Metformin 750 mg, and Metformin 1000mg.

The Metformin dose varies from person to person. The doctor shall prescribe these dosages as per your condition. The maximum dose of the medicine is 2000mg per day.

Read More: Vildagliptin and Metformin – Uses and Side Effects

Metformin Side Effects

Metformin’s Common Side Effects

Metformin common side effects

Some people may experience Metformin side effects. According to NHS, Some of the metformin’s most common side effects are as follows:

  • Continuous feeling of vomiting i.e. nausea
  • Complaint of diarrhoea. Metformin can cause indigestion problems and can thus cause metformin diarrhoea.
  • Bloating, gastritis, and heartburn issues.
  • Having stomach ache
  • Fever or chills
  • Sleepiness
  • Having unusual muscular pain
  • Decrease in the desire to eat
  • Having an unusual taste in the mouth

Generally, these metformin common side effects last for a few days. If they continue or they reappear again then seek the doctor’s help immediately.

Metformin Serious Side Effects

Metformin Serious side effects

Certain effects can cause health issues. One should not delay in seeking a health expert’s advice immediately. These metformin serious side effects include:

Lactic Acidosis

  • In a study conducted by Journal of Medical Case Reports, a serious side effect of metformin is metformin lactic acidosis. In this condition, lactic acid levels increase.
  • It is more common in patients with type-2 diabetes and with kidney problems.
  • Metformin increases anaerobic respiration by inhibiting cellular respiration. This causes lactate levels to increase.
  • Patients with renal issues are unable to clear accumulated lactic acid. This thus leads to lactic acid accumulation. This is metformin induced lactic acidosis.
  • This causes muscular pain, stomach problems, diarrhoea, trouble breathing, and a decrease in appetite. You feel tired and have sleeping issues.
  • Leaving lactic acidosis untreated can be problematic. Various health issues like heart problems, sepsis, liver damage, kidney damage, and even death can occur due to lactic acidosis.
  • Seek immediate help in case you find any of these symptoms.

Read More: How to Lower Blood Glucose Levels?

Allergic Reaction

According to the National Institutes of Health, metformin may cause allergic reactions, but it is not so common. Seek immediate health expert advice in case you notice any of the symptoms like:

  • Rashes on the skin or hives
  • Fast and irregular heartbeats
  • Swelling of throat or tongue
  • The severe form of dizziness. Headache. Some may complain of headaches after consumption of metformin
  • Shakiness and seizures
  • Trouble while breathing and chest discomfort. Feeling tightness in the chest


  • According to the findings of Oxford Academic, metformin hypoglycemia is seen in people who are also on insulin along with metformin.
  • Metformin lowers blood sugar levels. Sometimes overdose of metformin or metformin with insulin or its substitutes can decrease these blood sugar levels, resulting in hypoglycemia.
  • Hypoglycemia symptoms are trembling and shaky hands, sweating, feeling hungry, confusion, decreased focus, sleep, and difficulty concentrating.
  • Sometimes, improper diet, along with metformin, can cause hypoglycemia.
  • Measure your blood glucose levels before taking medicine. Measure the levels regularly after taking metformin. Don’t skip meals.
  • Take fast-acting carbohydrates to overcome hypoglycemia.
  • If your hypoglycaemic episodes continue, seek doctor’s advice immediately.

Anaemia-like serious symptoms

Metformin reduces vitamin B12 absorption. This results in vitamin B12 and iron deficiency. Left untreated can cause anaemia symptoms that can cause serious health issues. Some metformin less common symptoms similar to anaemia and vitamin B12 deficiency that require immediate health attention are:

  • Changes in the skin colour, yellowness
  • Feeling sleepy and dizzy
  • Difficult in concentration and decrease in reflexes
  • Depression and irritation
  • Dementia or memory loss.


Allergic reactions, lactic acidosis, hypoglycemia, and anaemia are some serious side effects of Metformin that require health experts’ attention.

Metformin Long-Term Side Effects

Metformin Long-Term Side Effects

Most of the long-term side effects known to be caused by Metformin are, in fact, due to poor management of diabetes. Metformin’s long-term side effect thus includes:

Anaemia and Vitamin B12 Deficiency:

  • People on metformin can feel symptoms of fatigue, dizziness, difficulty in walking, changes in skin colour, etc.
  • According to GOV.UK, this is because of vitamin B12 deficiency and iron deficiency. Metformin decreases vitamin B12 absorption, and this leads to anaemia.
  • Get regular blood check-ups. In this way, the monitoring of proper levels of vitamin B12 can be done.
  • If the levels of vitamin b12 are low, the health expert may suggest you take supplements or stop metformin.

Symptoms of Anaemia and vitamin B12 deficiency are:

  • Paleness of skin.
  • Having sore tongue and swelling of the tongue
  • decreased reflexes due to confusion
  • irritability and depression
  • decreased sense of smell
  • nerve damage and muscular pain.
  • difficulty while walking
  • memory or dementia-like symptoms

When taking metformin, you should ask your doctor about Vitamin B12 and Iron supplements.

Read More: Glucophage 500 MG Tablets to Control Your Blood Sugar Level

Metformin Side Effects During Pregnancy

According to Cochrane Library, metformin is generally safe during pregnancy and doesn’t increase the risk of birth defects. It’s especially preferred for managing gestational diabetes (GDM) in overweight women, as it helps control blood sugar without causing significant side effects.

If diet alone doesn’t meet glucose targets, metformin is preferred over insulin for GDM. For women with type 2 diabetes during pregnancy, metformin can be continued if they were already using it, with insulin added if needed.

According to NIH, starting metformin before pregnancy and continuing until term can benefit women with polycystic ovary syndrome (PCOS), reducing risks like gestational diabetes and preterm labor.

However, using metformin for non-diabetic pregnant women with obesity isn’t currently recommended due to uncertainties about its effectiveness and potential long-term impacts on childhood development, which require further study.

Metformin Warnings

While taking Metformin Brand name, it is necessary to know about metformin and other drug reactions, as well as health complications. The following are key warning points:

  • As advised by NHS, you should avoid taking Metformin with drugs like steroids, diuretics, Estrogen pills, and oral contraceptive medicines. These medicines reduce the metformin effect and thus make its usage ineffective.
  • Avoid using alcohol while taking metformin. Metformin, along with alcohol, may lead to lactic acidosis and serious health issues.
  • Avoid metformin during lactation. Metformin can pass through breast milk and thus reach the newborn. Thus, avoid metformin while breastfeeding.
  • Limit or avoid metformin in people with kidney and liver diseases. A kidney and liver test is necessary before taking the right amounts of Metformin.
  • People with breathing problems and circulatory problems should avoid Metformin usage.
  • People undergoing surgery, MRI scan or CT scan should inform the doctor on metformin usage. Anaesthesia before surgery can cause hypoglycemia. While iodinated contrast agents that are given before MRI and CT scans can cause risks of lactic acidosis.

Therefore, before using metformin discuss with your health expert about various health issues. Follow proper guidelines for usage, and in case of any issues, consult a health expert immediately.


Avoid metformin with kidney and liver disease, alcohol, steroids and diuretics before surgery, MRI, and CT scan.

Read More: Top 10 Homeopathic Medicine For Diabetes.

Risk Factors That Lead to Metformin Side Effects

Metformin side effects can be caused due to many risk factors. Some of the risk factors that could lead to metformin side effects are:

Renal Impairment:

Individuals with pre-existing kidney problems are at an increased risk of metformin side effects. Metformin is primarily excreted through the kidneys, and impaired renal function can lead to the accumulation of the drug in the body.

Liver Disease:

Liver impairment can affect the metabolism of metformin, potentially increasing the risk of side effects. Monitoring liver function is crucial to ensuring the safe use of metformin.

Advanced Age:

Elderly individuals may be more susceptible to metformin side effects due to age-related changes in kidney function. Close monitoring is essential to adjust dosage and prevent adverse reactions.


Conditions that lead to dehydration, such as severe illness, excessive alcohol consumption, or insufficient fluid intake, can heighten the risk of metformin-related lactic acidosis, a rare but serious side effect.

Heart Failure:

Patients with congestive heart failure have an elevated risk of lactic acidosis when using metformin. It is important to carefully assess and monitor these individuals to avoid potential complications.

Surgery or Imaging Procedures:

Temporary discontinuation of metformin may be necessary before surgeries or imaging procedures involving contrast agents, as these situations can increase the risk of lactic acidosis.

Excessive Alcohol Consumption:

Alcohol can potentiate the effects of metformin and increase the risk of lactic acidosis. It is advisable to limit alcohol intake and inform healthcare providers about alcohol consumption while on metformin.

Certain Medications:

Concurrent use of medications that interact adversely with metformin, such as some diuretics or antihypertensive drugs, can heighten the risk of side effects. Healthcare providers should be informed of all medications being taken to assess potential interactions.

Metformin General Issues, Piece of Advice and Metformin & Sleep Issues

Does metformin make you sleepy?

A common side effect of Metformin is that it can make you sleepy or feeling of dizziness. Seek health expert help if you have other problems like blurred vision, difficulty in concentration along dizziness. It can be due to hypoglycemia or a lowering of your blood glucose levels.

Metformin Insomnia

According to a study published by Oxford Academic, people with diabetes have problems with sleep patterns. This is because of variations in blood glucose levels. However, when a diabetic patient suffers from depression, it leads to insomnia problems. In such cases, metformin can induce insomnia further. Metformin insomnia is, therefore, an unwanted side effect of metformin. This side effect is noticeable within a few days of taking the medicine.

Metformin and Tooth Decay

Diabetes is linked with tooth decay. During diabetes, the bone resorption rate increases, and it causes bones to weaken. This can cause Periodontitis issues and tooth decay. Henceforth, dental care is highly essential for diabetes.

On the other hand, Metformin has proven to reduce the bone resorption rate. This helps in reducing bone decay. It thus helps in improving the results of surgical and non-surgical periodontal or dental therapy. Thus, Metformin does not cause tooth decay. Rather diabetes cases tooth decay.

Read More: Glycomet 500 Uses and Side Effects

Metformin and Depression

Can metformin cause depression?

According to the NIH, insulin resistance that causes diabetes is linked to anxiety and depression. In diabetes, fluctuating blood sugar levels result in sleeping disorders. These sleeping disorders, along with stress, induce depression. Thus, diabetes, along with stress, causes depression.

On the other hand, Metformin helps in reducing the effects of depression. It is clinically proven that Metformin treatment has antidepressant effects on diabetic patients. It also improves their cognitive function. Thus, metformin does not cause depression rather, it helps in treating depression in diabetic patients.

Bottom line:

Doctors use metformin as a drug to treat fluctuating blood glucose levels during diabetes. In women, it is used for treating polycystic ovary syndrome. Before taking Metformin treatment, you must provide all the health details to the doctor. You should take the right amounts of dosage and avoid taking overdoses. In case you notice any side effects of the medicine, seek health expert advice immediately.

Read More: Can you Reverse Type 2 Diabetes?

FAQ’s (Frequently Asked Questions)

How long do metformin side effects last?

The drug metformin’s common side effects are generally short-term. These last for 2 weeks. Long-term effects can last for months and sometimes years. But if common side effects reappear frequently, consult a doctor immediately.

Can metformin cause kidney problems?

A widely believed notion is that metformin can cause kidney problems. But metformin does not cause kidney damage. It is rather due to poor diabetes management that causes kidney problems. Metformin usage while already having kidney disease can cause further worsening of the disease. Thus, doctors ask for blood test and urine test before giving metformin to such patients. Otherwise, limit or avoid using metformin.

Can taking metformin cause diabetes?

Research regarding the effect of metformin in non-diabetic patients is still going on. But early research by and other clinical findings suggest that some drugs, like corticosteroids and beta-blockers, can cause diabetes. But in some cases, such drug-induced diabetes is reversible. While in some cases, it is permanent. Research suggests that metformin is useful in treating other health conditions apart from diabetes. For example, depression, weight management, polycystic ovary syndrome, etc. [6]. But to date, there is no evidence that metformin causes diabetes.

Last Updated on by Dr. Damanjit Duggal 


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