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Does Metformin Cause Insomnia (Resarch Summary)

by Dale Cudmore | Updated: Jan 23, 2022

Metformin is a very useful medication in treating diabetes for many people.

However, it can come with side effects. These side effects are usually limited to the gastrointestinal tract, including symptoms like stomach pain and diarrhea (1).

But there are some case studies and reports that suggest that metformin does cause insomnia in a few percent of users, along with a few other sleep related side effects like nightmares.

This post is a short overview of relevant research on metformin and sleep quality.

For Most People, Metformin Improves Sleep Quality

Since metformin improves insulin resistance, which improves blood glucose control, it can improve sleep for many diabetics.

When metformin leads to weight loss, it can improve sleep long term, since being overweight is one of the biggest risk factors for insomnia.

One paper that looked at type 2 diabetes patients taking metformin found that (2):

Total sleep time and sleep efficiency were higher in metformin-treated patients than in patients not treated with metformin (total sleep time: 6 h 39 min vs. 6 h 3 min, respectively; sleep efficiency: 77.9 vs. 71.5, respectively).

These findings were statistically significant and controlled for covariates like BMI.

Reports of Metformin Causing Insomnia

Insomnia isn’t known as a common side effect of metformin, but that doesn’t mean that it can’t happen. There just haven’t been any significant research trials on this subject.

However, one research paper that looked at reports of sleep issues while taking metformin observed that there are reported cases of insomnia (3):

The development of insomnia can be seen within a few days after starting metformin...In a web report, about 1.4% of people who observed side-effects when taking metformin had insomnia.

Even though 1-2% is a small number in this context, a lot of people have developed insomnia thanks to metformin use considering how popular the drug is.

SummaryWhile individual user reports aren’t exactly the gold standard of reliability, there does seem to be some compelling evidence that metformin can cause insomnia in a small percentage of people.

Why Would Metformin Cause Insomnia?

Since this topic hasn’t been studied in detail, the exact mechanism that causes insomnia in a small amount of people taking metformin is unknown.

However, there are a few potential reasons if we’d like to speculate:

  • Diabetic patients are already more likely to develop insomnia, introducing a new medication could cause stress and contribute to sleep issues.
  • Metformin affects blood glucose levels, which do play a role in sleep regulation (4). It’s possible that the body would adjust after a certain time period.
  • People with diabetes often take other supplements or medications that may have unexpected interactions.

Other Sleep Issues That Metformin Might Cause

Of all sleep issues reported from taking metformin, insomnia does seem to be the most common.

For example, one published case report tells the story of a 45 year old woman taking metformin for diabetes mellitus (5):

The woman received oral metformin 500 mg/day, every morning, for diabetes mellitus; on the third day following metformin ingestion, she experienced significant insomnia. One week later, she presented for metformin-induced insomnia. Metformin was replaced with glibenclamide, and her insomnia resolved.

Using an alternative medication as was done in that case study is a potential solution for patients who develop insomnia symptoms.

On top of insomnia, there are a few published case studies of metformin causing nightmares, although this seems to be a rare side effect (6).

One case study of a 56 year old patient reported him (7):

...experiencing nightmare and abnormal dreams directly after consumption of 750 mg extended release metformin. He noticed that the symptoms temporarily worsen when the dose was increased and felt better if he consumed metformin in the morning.

Changing the dosage or time when metformin is consumed may also be a solution to sleep issues if they arise.


  1. Metformin: A review of its metabolic effects
  2. The relationship between metformin therapy and sleep quantity and quality in patients with Type 2 diabetes referred for potential sleep disorders
  3. Metformin and sleep disorders
  4. Association between sleep duration and hemoglobin A1c level
  5. Metformin Insomnia: case report
  6. A therapeutic nightmare
  7. Nightmare and Abnormal Dreams: Rare Side Effects of Metformin?

Medical Disclaimer: The information on is not intended to be a substitute for physician or other qualified care. We simply aim to inform people struggling with sleep issues about the nature of their condition and/or prescribed treatment.

About the authorDale is the founder of Snooze University and a sleep researcher. I overcame my sleep issues and now I'd like to help you do the same by summarizing the latest sleep studies for you.