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As is the case with any other medication, there may be some instances where metformin interactions can occur. In such cases, use is not recommended, or usage will have to be adjusted in order to prevent or reduce the risk of negative interactions occurring from other drugs, medical conditions, or even food and drink.

Drug Interactions

According to the FDA, drugs that may interact with metformin include the following:

  • Cationic drugs

Please note that this list may not be complete, and other interactions with drugs not listed here may occur.

Metformin and Contrast (Intravenous Contrast)

Metformin medication does interact with intravenous contrast. It should be stopped prior to CT studies and withheld for at least 48-hours after. 

Metformin and B12

Some studies indicate that long-term metformin use could lead to B12 deficiency treatable with a supplement. Anyone taking metformin should check with their physician before taking a B12 supplement. 


There is no indication of an interaction between metformin and vitamin supplements. In some cases, supplements may be recommended while on this drug but should only be taken with the approval of a healthcare professional. 


In most cases, one should be cautious when mixing herbs with antidiabetic medications like metformin. Some herbs will work to lower blood sugar naturally and may have a positive influence or minimize side effects from the medication. Others may be contraindicated, although there are none listed for metformin. 


Lisinopril is a blood pressure medication often used in conjunction with metformin for those with both high blood pressure and diabetes. 


Some studies indicate that metformin and low-dose aspirin could have a positive effect when recommended by a physician. Aspirin doses over 81 mg, however, may interfere with how the body processes metformin and potentially lead to hypoglycemia or low blood sugar.


There are no known interactions between Tylenol (acetaminophen) and metformin. 

Food Interactions

Sometimes the foods we eat and the beverages we drink can also interact with our medications. Food and drink that may interact with metformin include:

  • Alcohol in large quantities

Please note that this list may not be complete, and there may be other foods and beverages that interact with this drug.

Metformin and Alcohol

For more information, please visit our page on metformin and alcohol interactions.

Disease & Conditions Interactions

Sometimes certain medications can increase the risk of negative side effects for patients with certain diseases or other medical conditions. According to the FDA, diseases and medical conditions that are known to negatively interact with metformin include:

  • Renal (kidney) disease
  • Liver disease
  • Metabolic acidosis

Please note that this list may not be complete, and there may be other diseases and medical conditions where patients should not take this medication.

Metformin and Dementia

There are conflicting theories on whether metformin use can increase the risk of dementia. Current studies indicate it does not cause dementia; in fact, it may help reduce the risk. Uncontrolled diabetes is, however, a risk factor for dementia. 

Some people do experience sleepiness and difficulty concentrating while taking this drug, though. 

Metformin and PCOS

Some PCOS patients do see benefits from taking metformin, including restored ovulation.

Metformin and Cancer

There was a recent FDA recall of the extended-release tablets 500 mg from multiple manufacturers. They may contain n-nitrosodimethylamine (NDMA), a potential carcinogen. Please contact your local pharmacist or physician for more information regarding the recall of metformin.

Metformin and Pregnancy

For more information, please visit our page on metformin and pregnancy risks.

Metformin and COVID19

Some studies indicate that those taking metformin may have a lower risk of dying from COVID-19. On the other hand, there may be a deadly interaction between some of the drugs being used to treat this infection and metformin. More studies are necessary in both cases. 

Metformin and Lactic Acidosis

Metformin use can induce lactic acidosis, a build-up of lactate, leading to a low blood pH. There is some indication that this drug may block a critical enzyme necessary to prevent the build-up. 

Other Interactions

Other possible interactions include the following.

Metformin and Kidneys

Taking metformin does not cause kidney damage. It is the kidneys that clear the drug from the body. That means that those whose kidneys do not function properly could end up with a potentially toxic build-up of the drug in their systems. 

Disclaimer: this article does not constitute or replace medical advice. If you have an emergency or a serious medical question, please contact a medical professional or call 911 immediately. To see our full medical disclaimer, visit our Terms of Use page.

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