Side Effects of Metformin

Metformin (also known by generic name Glucophage) is an oral hypoglycemic medication used to control high blood sugar. It is used in managing Type II diabetes, in the cases when the body’s high blood sugar levels cannot be properly controlled through exercise, diet and weight management alone. In some cases, patients use Metformin along with other anti-diabetic drugs like glyburide and insulin.

Metformin is the only drug of biguanide type (blood sugar controlling drugs) that has been allowed by US FDA and has been widely used as a to-go medication for Diabetes, as well as some other conditions (such as polycystic ovary syndrome, gestational diabetes, and others).

Metformin helps by reducing the amount of sugar, or glucose that is produced by the liver and also helps release the glucose from the liver into the body. The drug also helps to increase sensitivity to insulin by decreasing blood sugar production, reducing hyperglycemia, reducing triglycerides, improving transport of insulin and helping in weight management. In combination, all those factors lead to much-improved insulin sensitivity, which is especially helpful in cases of insulin resistance.

Another way metformin is helpful to diabetic and pre-diabetic patients is that is has been shown to slow down and reduce the absorption of carbohydrates through intestines, which further helps control blood sugar levels. It also increases the ability of muscles to absorb glucose so that the body can use it more productively. Metformin is particularly useful at keeping night-time glucose levels in check, although it helps maintain the levels all throughout the day as well.

Although metformin is often the go-to drug for diabetics and pre-diabetics, there are things you need to pay attention to when starting medicating with metformin. There are a few metformin side effects that some patients have experienced. Although generally very well-tolerated, different patients’ response to metformin may vary from one individual to another due to differences in body factors.

Most of the metformin side effects are the result of metformin preventing nutrient absorption in the GI tract, which by itself can cause a whole host of symptoms. This is why it is very important to watch your general state on metformin, consult with your doctor if anything is off, and take supplements to support and maintain your overall body health. A lot of metformin side effects can be curbed with proper supplementation as well as good diet.

Abnormal stools

This is one of the most common metformin side effects that a lot of people tend to experience when medicating with metformin. Generally, it is expressed in chronic diarrhea. It is believed to be related to that fact that metformin prevents enterocytes (cells in your digestive tract) from absorbing certain nutrients, particularly carbohydrates, which results in upset GI tract. 53% of the patients medicating with metformin experience diarrhea.

Changes in taste and smell

These common metformin side effects also happen because metformin alters your digestive process and your nutrient absorption. Some foods/products may start tasting and smelling better to you, while others may gain an unfamiliar/unpleasant smell/taste. Patients often report a heightened sense of smell on metformin, as well as metallic taste in the mouth and while consuming certain foods. 1-5% of the patients experience taste and smell disturbances while medicating with metformin.

Lactic Acidosis

Metformin can have an effect on the accumulation of lactates in your system, which results in a lower pH of your body. The symptoms of lactic acidosis may include general weakness, trouble breathing, abdominal pain, diarrhea, vomiting, muscle pain, and tiredness. About 3 out of 100 000 patients suffer from lactic acidosis while medicating with metformin.

The symptoms of lactic acidosis will be exacerbated in patients with excessive alcohol intake, heart issues, kidney issues, liver dysfunction. If you experience severe symptoms of lactic acidosis, it is recommended to stop taking metformin and talk to your physician.

Metformin side effects


Because nutrient absorption is hindered on metformin, you may develop deficiencies in such vital nutrients as Folic Acid, B12, CoQ10 and others, which can lead to tiredness, somnolence and possibly even anaemia. It is very important to keep your nutrients in check while on metformin. Consult with your doctor about supplementation.

Neuropathy (tingling or loss of feeling in limbs)

Metformin prevents vitamin B12 absorption which can cause symptoms of neuropathy such as tingling or loss of feeling in arms or legs. (Vitamin B12 helps support your body’s nervous system).

Memory issues and brain fog

This one is also a result of nutrient deficiency, particularly vitamin B12. Poorer vitamin B12 absorption may lead to loss of memory, difficulty in concentrating, brain fog, tiredness, etc. Some mood changes are also possible, such as moodiness, irritability, depression, anger, agitation and general instability.

To prevent these symptoms, try supplementing vitamin B12 on a regular basis. Dealing with a disease can be a stressful time. But do not discard mood or cognitive issues as it’s just as much an important part of your health as the rest of your body!

Muscle pain

Metformin can hinder COQ10 production in the body. CoQ1O is a coenzyme that is crucially important for muscle health (and energy production). Depriving your body of CoQ10 and other nutrients can cause muscle stiffness, pain, and cramping.

Nausea and vomiting

Metformin causes general GI tract upset and nausea and vomiting is a part of it. Unfortunately, as many as 26% of patients report nausea and vomiting as two of metformin side effects. To help curb nausea, try to take metformin with your largest meal of the day and try to include some protein with that meal.

If you feel like you can’t eat a thing and just really feel too sick, still try to eat something, maybe something small – you will very likely feel better. If you can’t seem to curb the symptoms, talk to your physician. Some patients report better tolerance of Glumetza brand of metformin which is a little more expensive and has a different formulation that is often better tolerated.

Skin and hair issues

Depletion of nutrients such as vitamins B12, B9, B6, Folic Acid, and others may lead to a worsened condition of your hair and nails. Your doctor may recommend the nutrients that are best to supplement to avoid further aggravation of the condition and improve your overall state.

Difficulty breathing 

1-5% of patients experience shortness of breathing on metformin. It is recommended to talk to your physician if you have this symptom.

Flu-like symptoms such as muscle pain, fever, chills, and weakness

All of these can be symptoms of lactic acidosis and it is highly recommended to pause medicating with metformin and address the concern to your doctor if you have these symptoms.

Other metformin side effects may include the following:

Chest discomfort

Heart palpitations

Lightheadedness or dizziness

Nail problems

Feelings of a rapidly or forcefully beating heart (heart palpitations).

Flushing (a skin reddening, commonly on the face)

Increased sweating

Increased thirst

Metformin Side Effects

A few other complications while taking metformin can be:

Signs of allergic reaction, including unexplained skin itching, rash, wheezing, or difficulty in breathing, hives, or unexplained swelling.

Lactic acidosis in patients with kidney problems. Lactic Acidosis can be sudden and severe, especially in patients with kidney issues. Lactic acidosis takes place when there is an increased level of lactic acid in the body of the diabetes patient.

While the drug is used in inhibiting the process of hepatic gluconeogenesis (the process that produces glucose), it also reduces the intake of lactate by the liver.

The problem often arises in individuals with impaired renal functions taking metformin. The drug and lactate will then build up to cause lactic acidosis. Although the incidence is just 10 in every 100,000 people, you should still consult your doctor about using metformin if you have a known kidney condition.

Metformin may cause severe Vitamin B12 deficiency. Around 7 out of 100 patients are likely to experience a largely reduced level of Vitamin B12 while medicating with metformin. Luckily it’s relatively easy to monitor the levels of B12 to know whether or not Vitamin B12 injections would be necessary.

Metformin can also cause impaired kidney and liver functions. This can happen if a patient takes an overly large dose of the drug, which can make it hard for the liver to process it. Kidneys will also be affected. In extreme cases, it is possible for the kidney and liver to fail completely, leading to a lot of complications in the patient. Be very careful about dosage when it comes to metformin.

Metformin is capable of affecting the level of certain hormones in the body, especially in large doses. For instance, an overdose may lead to a reduction in the blood levels of thyroid-stimulating hormones, especially if the individual has a history of suffering from hypothyroidism. It can also cause a reduction of the blood level in testosterone and luteinizing hormones found in men.

Metformin side effects in womenApart from diabetes, metformin is also used to treat (PCOS) or Polycystic ovary syndrome.

According to FDA, metformin is safe for pregnant women. There is no evidence of an increase of human fetal abnormalities as a result of metformin use during gestation. For instance, in women, Metformin has been used to treat non-insulin-dependent diabetes, with no increase in the occurrence of major congenital anomalies.

However, do make sure to consult your physician and/or obstetrician before going on with metformin. It is crucial to receive qualified medical advice which will take into account your general health state, your previous concerns and all the other factors which may play a role in your baby’s successful development.

In the case of infertile women suffering from Polycystic Ovary Syndrome (PCOS), the drug should be used after the doctor has carried out a careful analysis and synthesis of the information obtained from a detailed physical examination, history and the results of series of investigations undergone by the couple.

The type of infertility (primary or secondary) should be taken into account, the duration of infertility, menstrual history (dyspareunia, dysmenorrhoea, discharge), medical and surgical history, sexual history (coital frequency), social history and drug history (smoking, alcohol, occupation).

One of the most common Metformin side effects is weight loss. Metformin can lead to a loss of appetite in patients, thus making the weight loss goal a reality for the patient. (A major goal of diabetic patients is a weight loss since the major symptom of Type II diabetes is excess weight.)

The weight loss aspect of Metformin does not mean that the drug should be taken by everyone who wants to lose a few pounds. The drug will also not be effective if the patient continues consuming foods that cause an increase in blood glucose level since such rapid increase forces the body to create insulin before the drug can have any effect.

If at any point in your journey the side effects of metformin become too much to live with, do consult your doctor to get professional medical help and advice. They might review your dosage and potentially decrease it to curb some of the symptoms. Your doctor may also prescribe you a different formulation of the drug, maybe a slower-releasing for of it, to help stabilise your symptoms.

To help with some of the symptoms, try taking your metformin with a larger meal containing protein. Do not take metformin on an empty stomach. If you take metformin once a day, the best time would be at dinner time as it’s close to the night -time when you can sleep through the worst of the symptoms.

Don’t give up on your medical plan if you need metformin. You will be able to feel better with time when you know more about your individual tolerance and develop your own ways of taking the medication with the best results.

Talk to your doctor about supplements. Metformin does hinder absorption of many vital nutrients in your body, which can lead to a whole host of symptoms that can be hard to deal with. This can be corrected with proper diet and a good supplementation plan.

You will likely have to supplement such nutrients as vitamin B12, B9, CoQ10, and Folic acid. Your doctor will advise you on what else you can do to improve your overall health while tackling your diabetes.

Regardless of the side effects of Metformin, it’s still a widely used, effective and a leading anti-diabetic drug. If you are concerned about these side effects or they became more severe over time make sure to discuss it with your doctor. Also, remember not to lower or increase your Metformin dosage as a result without consulting your doctor first.

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