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Metformin Side Effects: What are They and How Long Do They Last?

Metformin Side Effects: What are They and How Long Do They Last?

About one in every ten Americans are suffering from some form of diabetes, while an additional one out of every three adults, or 88 million people, have prediabetes. Poor lifestyle choices, including the prevalence of obesity, diets that are high in calories and carbohydrates, and sedentary lifestyles have contributed to a considerable rise in the prevalence of Type 2 diabetes. The American Diabetes Association estimates that approximately 34.2 million Americans have diabetes, and roughly 31 million people in this group are diagnosed with Type 2 diabetes. Type 2 diabetes is a condition in which the body produces insulin but is resistant to the hormone’s effects, often as a result of the patient’s lifestyle. Although all patients with Type 2 diabetes are likely to be prescribed lifestyle changes as part of their treatment plan, some patients may need to take medications like metformin to manage their blood sugar levels. Although metformin is intended for long term use, it can cause significant side effects that can last for varying amounts of time, depending on the patient.

Overview

Metformin is a prescription medication that is used primarily for the treatment of Type 2 diabetes. The medication is part of a class of drugs called biguanides and has been prescribed to over 120 million people around the world, making it the most popular drug for the treatment of Type 2 diabetes. Biguanides like metformin help patients with Type 2 diabetes to regulate the amount of sugar in the blood by increasing insulin sensitivity. With increased insulin sensitivity, the body is better equipped to use blood sugar for energy, which helps to regulate the amount of glucose in the blood. Metformin is a generic drug, but it is also sold under several brand names, including Glucophage, Glucophage XR, and Riomet. The drug is available in both instant release tablets and extended-release formulas.

Conditions Treated

Metformin is primarily used to treat Type 2 diabetes, but it is also used off-label for the treatment of polycystic ovarian syndrome (PCOS). Type 2 diabetes, also known as Type 2 diabetes mellitus, affects more than 90 percent of Americans that have been diagnosed with diabetes. An additional 88 million people are estimated to be prediabetic, and the majority are unaware of their condition. While Type 1 diabetes is characterized by insufficient production of insulin, Type 2 diabetes is characterized by insulin resistance. Regardless of which type of diabetes a patient has, the body is unable to properly process the sugars consumed in food and convert them to energy.  Under normal circumstances, the body breaks down the food we consume into glucose, which is released into the bloodstream. As our blood sugar levels increase, the body releases a hormone called insulin from the pancreas; this hormone directs the body to use the blood sugar for energy.  Patients with diabetes are unable to use the blood sugar for energy because they either do not produce enough insulin, as is the case with Type 1 diabetes, or they are resistant to its effects, which occurs with Type 2 diabetes. When the blood sugar levels remain high for an extended period of time, they can cause serious health issues.  Serious conditions and complications associated with high blood glucose include:

  • Increased risk of kidney disease
  • Increased risk of heart problems like heart failure and heart attack
  • Nerve damage in the feet and hands (neuropathy)
  • Damage to the blood vessels of the eyes (retinopathy)

While metformin is most commonly used for the treatment of Type 2 diabetes, it is also used off-label for the treatment of polycystic ovarian syndrome, or PCOS. PCOS is a condition with many coexisting symptoms that can impact fertility, including elevated insulin levels. Metformin can be used to normalize insulin levels and improve insulin sensitivity, which helps to reduce the risk that women with PCOS will experience diabetes. Metformin can also prevent some of the weight gain that is commonly caused by PCOS, which helps to prevent diabetes as well, particularly in patients who have already been diagnosed with prediabetes. 

Metformin Side Effects

Although metformin is associated with a significant number of side effects, it does report fewer side effects than other Type 2 diabetes and prediabetes medications. However, the side effects caused by metformin, particularly gastrointestinal side effects, can cause a significant quality of life issue for some patients, leading to the low adherence rate for the medication. Common side effects of metformin that typically do not require medical attention include:

  • Diarrhea
  • Bloating
  • Gas
  • Constipation
  • Stomach pain
  • Heartburn
  • Nausea or vomiting
  • Headache
  • Weight loss
  • Unpleasant metallic taste in the mouth

Diarrhea is the most commonly experienced side effect of metformin, while nausea and vomiting are also common. Most common side effects of metformin are experienced when a patient first begins taking metformin or when their dose of the medication is increased. It is common for many side effects to disappear or diminish in intensity as the patient’s body adjusts to the medication, but this is not always the case. While most side effects will dissipate in about two weeks, some patients experience troublesome side effects for much longer, including months or even years. While such a prolonged experience with side effects is uncommon, patients should report any side effects that become intolerable or last for an extended period of time to their healthcare provider. It may be able to avoid or minimize certain side effects by switching from the immediate release form of the drug, which is more likely to cause side effects, to the extended release version. Side effects may also be improved by taking metformin with a large meal, which slows absorption of the drug by the body.  

While most side effects of metformin are inconvenient rather than dangerous, some side effects are more serious and require immediate medical attention. Although rare, these side effects can be very dangerous if not treated immediately. The most serious side effects associated with metformin are lactic acidosis, anemia, and hypoglycemia.

Lactic acidosis is a medical condition caused when the body overproduces or underuses lactic acid, which causes the pH of the body to become unbalanced. Lactic acidosis is treatable if caught early, but it can be fatal if not addressed. It is believed that metformin can contribute to lactic acidosis as it builds up in the blood. Patients with kidney disease, kidney problems, liver disease, excessive alcohol use, heart problems, or surgery or radiology procedures that use iodine contrast are more likely to experience lactic acidosis. Symptoms of lactic acidosis include:

  • Weakness
  • Feeling cold
  • Flushing or sudden reddening and warmth of the skin
  • Nausea
  • Trouble breathing
  • Lightheadedness
  • Fast or slow heart rate
  • Muscle pain
  • Stomach pain with any of these symptoms
  • Extreme fatigue
  • Decreased appetite
  • Vomiting
  • Dizziness

Anemia, or low levels of iron in the blood, is a condition characterized by low levels of red blood cells, which carry oxygen to the different parts of the body. When used for an extended period of time, metformin can cause a vitamin B-12 deficiency, which can cause anemia in some circumstances.  Common symptoms of anemia and vitamin B-12 deficiency include:

  • Tiredness
  • Dizziness
  • Lightheadedness

Low blood sugar, or hypoglycemia, can occur when patients who take metformin eat a poor diet, exercise strenuously, take other diabetes medications, or drink alcohol excessively. Using metformin alone will not cause hypoglycemia in the absence of other factors. Symptoms of hypoglycemia include:

  • Weakness
  • Nausea
  • Vomiting
  • Dizziness
  • Abnormally fast or slow heartbeat
  • Stomach pain
  • Lightheadedness
  • Tiredness

Sources:

https://www.healthline.com/health/diabetes/metformin-side-effects 

https://www.healthline.com/health-news/why-so-many-people-with-diabetes-stop-taking-metformin 

https://www.cdc.gov/diabetes/basics/type2.html 

https://www.cdc.gov/diabetes/basics/diabetes.html 

https://www.diabetes.org/resources/statistics/statistics-about-diabetes 

https://medlineplus.gov/druginfo/meds/a696005.html 

https://www.verywellhealth.com/biguanides-diabetes-medications-1087355 

https://www.tandfonline.com/doi/full/10.3109/10717544.2015.1089957 

https://dom-pubs.onlinelibrary.wiley.com/doi/abs/10.1111/dom.13160

https://spectrum.diabetesjournals.org/content/19/4/202#:~:text=Procainamide