Does Metformin Cause Constipation?

Written by Abby Hill
3 mins, 37 secs Read
Updated On August 24, 2023

Metformin may give rise to constipation in roughly 1% of patients. On the other hand, it is more common for Metformin to result in diarrhea in comparison to constipation. Think of other reasons behind the occurrence of constipation, including diabetes itself. In this article, the association between constipation and Metformin is explained. Constipation during the treatment with an antidiabetic drug, Metformin is not always owing to the medicine. Other concurrent conditions might also be responsible for such problems.

Does Metformin Result in Constipation?

Metformin hardly ever causes constipation. As per the research, below 1% of patients receiving Metformin get the problem of constipation. The occurrence of diarrhea resulting from Metformin is up to 53% of patients consuming the immediate-release form of Metformin. The occurrence is much lesser as compared to the extended-release formula (i.e., around 10%).

Metformin less commonly leads to side effects i.e., constipation. The incidence of constipation was seen to be roughly 1% in the extended-release (ER) form of Metformin and roughly 0.6% in the immediate-release (IR) form of Metformin. Side effects of the Metformin ER are milder. This form can be consumed once a day rather than twice a day like the regular form. A person is then less likely to experience diarrhea and nausea.

Constipation is termed as having fewer than 3 bowel movements weekly. Stools are frequently hard, dry, or clumpy. Moreover, constipation is linked to other abdominal signs including distension or bloating (majorly on the left side).

Having a constipated belly during therapy with Metformin might be because of other reasons as well. Metformin can be suspected as a reason for constipation if a person starts experiencing it soon after consuming the drug. If the development of constipation occurs later after months or years of Metformin intake, it is a good idea to go for an optional cause of constipation excluding Metformin.

How does Metformin work?

Metformin aids a person’s body to make use of its insulin in an improved manner. It does this by reducing the quantity of glucose the liver manufactures. This consequently reduces blood glucose levels. Metformin comes up with its 2 benefits over other anti-diabetes medications:

  • There is a lesser risk of a drop in the levels of blood glucose with this medicine. 
  • It does not lead to weight gain. However, just like any drug, Metformin may result in side effects.

If a person is type 2 diabetic, the doctor most probably prescribes Metformin, to begin with. Here are a few side effects of this medicine that a person should be familiar with.

  • Digestive problems: About 25% of diabetes experience digestive issues like acidity, bloating, abdominal pain, diarrhea, and constipation. Every so often these side effects go on their own. 
  • Lack of Vitamin B12: In the absence of satisfactory amounts of B12, the risk of peripheral neuropathy enhances. This is a tingling or numbness sensation in the patient’s feet and legs. If a person is already at risk of diabetes, he or she must also check B12 levels frequently. The levels of B12 should be kept naturally high by having chicken, beef liver, eggs, fortified cereals, or dairy products.
  • Lactic Acidosis: Patients taking Metformin may have a build-up of lactic acid, a chemical that the person’s RBCs and muscles make naturally. It’s more expected to occur in individuals whose kidneys fail to work properly and fail to clear Metformin from the body.

What are the Other Likely Reasons for Constipation with METFORMIN?

Constipation is measured as a rare side effect of Metformin. Hence, it is good to think of other reasons for it. Having constipation while on Metformin treatment for diabetes might arise from a range of diabetes-associated factors. It makes sense to think of other reasons for constipation if it has developed after months or years of treatment with Metformin.

Possible optional reasons for constipation during Metformin intake may include:

Diabetic Neuropathy (Diabetes-Induced Constipation)

There is a set of nerves responsible for controlling gut motility; they are referred to as ANS (autonomic nervous system). Nerve damage may result due to long-lasting or unregulated diabetes or high sugar levels. When the nerves that control bowel motions get damaged, bowel motility would become slower. Therefore, a person would get constipation while suffering from diabetes. Around 50% of diabetics have nerve damage (diabetic neuropathy).

Low-Calorie Consumption and Dehydration

If a person is consuming Metformin for diabetes, he or she possibly follows a strict diet plan to regulate his or her glucose levels. But, low consumption of overall calories and low fiber consumption is a well-identified risk factor for constipation. Furthermore, if the person’s sugar levels are uncontrolled, he or she may experience increased urine output. Frequent urination eventually brings about dehydration, which can be another risk factor for constipation.

Other Medicines that are Consumed with Metformin

People with diabetes are always poly-medicated as they might have other chronic problems like hypertension. Moreover, several other medicines are more expected to bring about constipation than Metformin. These medicines can be:

  • Blood pressure-lowering medicines like Calcium Channel Blockers (Amlodipine).
  • Antidepressants used for diabetic nephropathy. 
  • Antihistamines.
  • Analgesics (mostly NSAIDs may result in constipation).
  • Iron supplements.
  • Antacids.
  • Anti-spasmodics.


It’s always better to discuss with a healthcare provider if a person experiences unexplained constipation. Too many conditions or ailments may bring about constipation while on Metformin treatment. Don’t stop the medicine due to constipation without medical consent from the concerned doctor. This might cause worsening diabetes (if the medicine is being taken for diabetes).

Author: Abby Hill