During a recent diabetes class Maria, newly diagnosed with type 2 diabetes, said “What the heck is metformin? Everyone I know is taking it. I’ve started calling it Vitamin M because it’s more common than Vitamin C supplements!”  This made us all laugh out loud as we recognized the truth in that observation. 

Metformin is an important antidiabetic agent that is widely used for patients with diabetes and has also been effectively used with patients who are at risk of diabetes. Based on the American Diabetes Association 2019 Standards of Medical Care in Diabetes, “Metformin, if not contraindicated and if tolerated, is the preferred initial pharmacologic agent for the treatment of type 2 diabetes.” Metformin has been on the market in the United States since 1995. With this long history of use, we know a lot about how metformin works and how people respond to this valuable medication.

How does metformin work?

Metformin works in several ways to reduce blood sugars:

1. Metformin reduces the amount of sugar produced in the liver and released into your bloodstream. Before you had diabetes, your liver would release sugar into your blood stream to prevent you from dropping too low; now that you have type 2 diabetes, your liver does not get the message to stop making sugar when blood sugar is already high. Metformin helps correct this problem, and slows liver sugar production.

2. Metformin also improves muscle insulin sensitivity. When you have type 2 diabetes, your insulin doesn’t work as well as it did before diabetes.  Insulin is needed to move sugar from the blood into the muscle cell where it can be used for energy.  When insulin isn’t working well, the sugar lingers in the blood stream, wreaking havoc on your blood vessels. Metformin helps get the sugar to its proper destination, into your cells.

3. Metformin also decreases intestinal absorption of glucose.

Metformin may help with weight loss.  Although it is not a weight loss medication and the research does not indicate a big impact on weight loss, we DO know it is NOT associated with weight gain.  By contrast, some diabetes medications ARE associated with weight gain.  That’s a significant plus because we know the last thing most people need is to gain weight from your diabetes treatment.

Metformin may also provide some cardiovascular benefit.  Although, this benefit is not the primary function of metformin, it’s a happy little extra.  Research shows that metformin can reduce the risk of dying from heart disease, lower LDL cholesterol, plaque accumulation and weight.

What are common side effects of metformin?  Does taking extended-release metformin help?

The most common side effects of metformin are gastrointestinal disturbances such as nausea, vomiting, gas, diarrhea, and stomach upset.  

Taking metformin with a meal can reduce these symptoms.  Starting at a low dose and gradually increasing over time can also help.  That’s why your physician may prescription 500 mg to start, and increases to 1000 or 2000 mg over several visits.  It doesn’t mean that you have done anything wrong or that your medication isn’t working, it’s simply a strategy to help you feel more comfortable.  Many people who are bothered by metformin at first find that these symptoms gradually decrease with time; and some people find these symptoms never improve.

The extended-release metformin can decrease these side effects and the once-daily dosing is more convenient and may results in fewer missed doses.

Are some people allergic to metformin?

Metformin allergy is extremely rare.  However, similar to other drugs, allergy to metformin may occur.  If you suspect you are having an allergic reaction, talk to your doctor right away or go to the nearest emergency room. 

Who shouldn’t take metformin for diabetes?

The two most common reasons that patients should not take metformin include: intolerance and kidney damage:

Patients who do not adjust to, or cannot tolerate, the gastrointestinal disturbances would be switched to another medication for blood sugar control. 

Diabetes can cause damage to our kidneys, and when our kidneys start to show this damage, your doctor will recommend you change to another medication for blood glucose control.  That is not to say that the metformin caused the damage, rather, once you have reached a certain level of damage, you cannot take metformin anymore.