This Is How Long It Takes For Metformin To Start Working

Metformin, sold under various brand names like Glucophage, is a common medication used to improve high blood sugar levels, often triggered by type 2 diabetes (via Mayo Clinic). The Food and Drug Administration (FDA) approved the medication as an effective diabetes treatment in 1995. According to Healthline, the drug has been prescribed to over 120 million people worldwide since its approval. Metformin's mechanism of action is to lower the amount of glucose absorbed by the intestines, decrease how much is made by the liver, and improve insulin sensitivity or resistance, per Besides improving insulin resistance, Diabetes UK reveals that metformin might help reduce your vulnerability to diabetes-related heart diseases. However, the source notes that starting the medication can be overwhelming at first and the treatment is continuous, meaning there's no end date.

If you've been prescribed metformin, you might be curious about how long it takes to start working and the common side effects associated with the drug's usage. Continue reading for more information.

How long does it take for metformin to start working?

A 2021 study published in the journal Frontiers in Pharmacology writes that metformin is available in both long- and short-acting forms. Medical News Today states that people usually notice changes within 48 hours after beginning use; however, metformin may take four to five days for effects to fully actualize. They further note that the timing depends on the dosage.

As a drug's onset of action depends on various factors, including drug interactions, the U.S. Food & Drug Administration (FDA) advises metformin users to be forthcoming with their medical history and other medications they may be taking. The FDA also says some medications may become less effective and even lead to harmful side effects when they interact with other drugs.

Generally speaking, the best way to take metformin is to consult your doctor for a prescription and appropriate usage instructions. Mayo Clinic also states that doctors prescribe your metformin dosage based on various factors, including the medication's form and your specific medical conditions.

Common side effects of metformin

As mentioned earlier, it's important to be forthcoming with your doctor about any other medications you're taking in order to reduce your risk of metformin side effects. According to, metformin can interact with 355 other drugs, with about 19 of these drug interactions being major. The source also indicates that excessive alcohol should be avoided and the drug should be taken with meals. The National Health Service (NHS) further notes that around 1 in 100 people experience common side effects, including nausea, diarrhea, stomach ache, and loss of appetite due to an unexplained metallic taste in the mouth. The cause of diarrhea and other stomach symptoms is further explained in a 2021 study published in the journal Clinical Diabetes. The study attributes these symptoms to changes in the gut microbiome, which protects the body from pathogens. The source also explains that metformin usage increased intestinal glucose and bile acid turnover and GLP1 concentration levels causing diarrhea and other stomach-related symptoms.

Healthline additionally states that metformin can decrease vitamin B12 levels, making you vulnerable to anemia or low levels of red blood cells. Some metformin users may also develop hypoglycemia, especially if they combine the drug with a poor diet, strenuous exercise, alcohol, or other diabetes medications. Lastly, metformin can rarely cause users to experience behavioral changes similar to being drunk and drowsiness, per Therefore, it's vital to be extra vigilant when driving, handling heavy machines, or undertaking tasks that require significant alertness.