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Does metformin cause dementia?

Metformin is a popular prescription medication used to treat Type II diabetes. The effect of metformin, a biguanide drug, is to reduce the amount of sugar in a person’s blood. Ever since metformin hit the market, there have been many myths about its connection to dementia, a disease associated with confusion, memory loss, and mood changes. In this article, we’re going to take a closer look at the link between metformin and dementia. Is there a connection? If so, what is it? 

What is dementia?

First, let’s take a closer look at what dementia is. Dementia is a term used to describe diseases and illnesses that result in problems like memory loss and issues with speaking and thinking. One type of dementia is Alzheimer’s, which typically affects older adults. Alzheimer’s disease is a neurodegenerative disease that is the most common cause of dementia, followed closely by vascular dementia. Alzheimer’s disease works by deteriorating the nerve cells in the brain. Like Alzheimer’s, Parkinson’s disease is another well-known condition that can cause incident dementia. 

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Is metformin linked to dementia?

The simple answer is that metformin does not cause dementia and can actually help lower a person’s dementia risk, says Verna R. Porter, MD, a neurologist and director of Dementia and Alzheimer’s Disease Programs at Providence Saint John’s Health Center in Santa Monica, California. “In fact, a recent study of 17,000 veterans with diabetes found that taking metformin was associated with a lower risk of dementia than other diabetes drugs known as sulfonylureas (like glyburide and glipizide),” Dr. Porter says.

Another study also highlighted that the cognitive function of specific racial groups could benefit from metformin. It showed that metformin use was associated with reduced rates of dementia and improved cognitive function among African American patients with Type 2 diabetes (hazard ratio [HR] = 0.73; 95% confidence interval [CI], 0.6-0.89) but not white patients (HR = 0.96; 95% CI, 0.9-1.03). 

That said, other studies indicate a different link between diabetic patients’ long-term use of metformin and other insulin sensitizers and the incidence of dementia. Some cohort studies show an increased risk of developing dementia when using metformin. 

In other words, the current research into the link between metformin use, especially as monotherapy, and a dementia diagnosis, is mixed and not yet definitive. More clinical trials and observational studies are needed. 

RELATED: Diabetes medications and treatment

Can metformin cause memory problems?

The research is unclear at this time if metformin can cause memory problems, so there isn’t a definitive answer. However, many doctors still recommend metformin as a first-line treatment for Type II diabetes. 

What may be causing memory problems for those taking metformin is not the medication itself, but the underlying illness: diabetes. The mental health effects of diabetes can range from mild cognitive impairment to severe. In fact, a 2011 clinical study illustrated a risk factor between Type 2 diabetes mellitus and dementia, stating that type 2 diabetes increases the risk of dementia more than two-fold. 

Another study from 2017 made a connection between insulin resistance—a trait of diabetes—and long-term cognitive decline. 

The bottom line is that more research is required to get conclusive answers on how metformin contributes to memory problems, however, the underlying condition that metformin treats—type 2 diabetes—certainly can lead to decreased cognitive function and memory issues. 

What are the side effects of long-term metformin use?

Often when people are prescribed metformin for diabetes care, they’re in it for the long haul, so there are long-term side effects to consider. 

These are the most common side effects of metformin:

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

Often these common side effects will go away within a few days or weeks, especially if they are mild. Sometimes there is a reduced risk of these mild side effects when taking metformin with a meal. However, severe side effects may require immediate medical advice from a healthcare provider. They’ll advise you on the best course of action and follow up accordingly. 

Below is a list of more serious side effects of metformin that require urgent medical attention.

Lactic acidosis

This life-threatening condition occurs when there is a dangerous build-up of lactic acid, along with decreased pH and electrolyte disturbances in the body. It happens if the kidneys are not functioning properly, and therefore are not properly excreting metformin. Long-term diabetes can lead to kidney problems, resulting in a build-up of metformin in the body, which creates lactic acidosis. The likelihood of developing lactic acidosis increases in patients with heart disease or congestive heart failure. 

Symptoms of lactic acidosis to look out for include:

  • Tiredness
  • Weakness
  • Unusual muscle pain
  • Trouble breathing
  • Unusual sleepiness
  • Stomach pains, nausea, or vomiting
  • Dizziness or lightheadedness
  • Slow or irregular heart rate

Hypoglycemia (low blood sugar)

On its own, metformin will not cause hypoglycemia. However, in very rare cases low blood sugar can occur if combined with poor diet, strenuous exercise, drinking too much alcohol, or other antidiabetic drugs. Left untreated, hypoglycemia can cause some people to pass out, have a seizure, and in worst cases, lead to permanent brain damage.

The following are symptoms of low blood glucose levels:

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


Anemia is a low count of red blood cells, which can be caused by low levels of vitamin B12. Since metformin can cause a vitamin B12 deficiency, it’s essential that patients take either a vitamin B12 supplement or ensure they’re ingesting enough through their diet. 

Symptoms of anemia include:

  • Lightheadedness
  • Dizziness 
  • Tiredness
  • Pale skin
  • Cold hands and feet
  • Brittle nails

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Before you stop taking metformin

Once someone starts taking metformin, it’s important to consider the risks of stopping the medication abruptly. Patients should always speak with their doctor before stopping any medication as there is a chance their symptoms or condition could worsen. A doctor will determine the safest way to transition to another antidiabetic medication, such as a sulfonylurea, or advise how to create necessary lifestyle changes. 

RELATED: Your guide to reversing prediabetes with diet and treatments

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