Is Metformin an Effective Treatment for Type 2 Diabetes?

What It Does and How to Take It

In This Article

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If your doctor has prescribed Metformin for diabetes or another use, what exactly is this medication and how does it work? What is the best way to take it to reduce side effects? What adverse effects might you experience and why is it important to be aware of these?


According to the American Diabetes Association Standards of Care, Metformin, if tolerated, is the preferred initial oral diabetes medication for Type 2 diabetes because it is the most effective. Unlike people with Type 1 diabetes, people with Type 2 diabetes make ​insulin. The problem is that they are either not making enough insulin or the insulin they do make isn't being used efficiently. Metformin is a weight neutral medication that helps the body use insulin. Weight neutral means that it is not associated with weight gain (or loss) as are many other diabetes medications.

Like all medicines, however, Metformin can produce some side effects, some of which it is important to know.

How It Works

Metformin belongs to a class of drugs called biguanides, which are derived from the French lilac. Metformin helps to lower blood sugar by utilizing insulin and reducing insulin resistance (making your body more sensitive to insulin.)

Many people with Type 2 diabetes carry excess weight—fat cells prevent insulin from doing its job, ultimately causing the cells to become resistant to insulin. When cells become resistant to insulin, insulin is unable to direct sugar from the bloodstream to the cells to use for energy, and instead, the sugar remains in the blood.

As a result, the liver responds by making more sugar because it thinks the body needs it for fuel and the pancreas responds by making more insulin. You wind up with chaos—high blood sugars and high insulin levels. Metformin helps to restore normalcy by increasing insulin sensitivity and reducing the production of sugar made by the liver.

Other Uses

In addition to being used for diabetes, metformin is sometimes used "off-label" in polycystic ovary syndrome (PCOS) as an aid in fertility, as a weight loss adjunct, or to treat gestational diabetes. Research is currently evaluating the possible increased survival of those with several cancers such as lung cancer, breast cancer, and bladder cancer who have been treated with metformin. Other studies have found that metformin targets many pathways in the growth of cancer. Metformin is also being studied for its effect on thyroid as it appears to reduce the risk of goiters, thyroid nodules, and thyroid cancer.

When You Should Take It

It is recommended that people take Metformin with meals as this both increases its absorption in the stomach and reduces side effects—stomach cramps, diarrhea, and nausea. Typically, most people new to Metformin will take it with the largest meal. To remember to take Metformin, you should try to take it around the same time(s) every day.

Starting Metformin

Metformin is a medicine that should be increased or titrated gradually to ease any stomach discomfort when it is first started. How long this takes will depend on what your health care provider prescribes and how you respond to the medication (the medication has several doses).

For example, a person who is new to Metformin and has been prescribed 2000mg twice a day may start by taking 500mg once daily with dinner for one week. At week two, she will take 500mg with breakfast and 500mg with dinner. At week three, she will take 1000mg with dinner and 500mg with breakfast. And at week four, she will be her therapeutic goal—taking 1000mg with breakfast and 1000mg with dinner.

Throughout the duration of titration, you should monitor your blood sugars. If you experience low blood sugars or any other side effects, you should contact your health care provider so that the medication could be adjusted accordingly. When in doubt—always ask.

Side Effects

The biggest complaint people have about Metformin is that it causes gas and diarrhea. This can often be reduced by increasing the dose gradually. If you do experience diarrhea or gas, make sure to contact your healthcare provider to make sure you are taking the medication correctly.

If you are experiencing persistent side effects such as gas or diarrhea, ask your healthcare provider about the extended release version of this medicine—it is a time released version of the medicine which may help to prevent the gastrointestinal side effects. The extended release version is usually taken once per day with the evening meal.

Other Side Effects of Metformin

Unlike many treatments for diabetes, Metformin does not cause hypoglycemia (low blood sugar.) Also, unlike many type 2 diabetes medications, Metformin does not cause weight gain and may even assist with weight loss.

Some side effects of Metformin can be more serious. One of these effects is lactic acidosis. Though the latest studies suggest this is an uncommon condition which may not be directly associated with Metformin, the risk of lactic acidosis is increased in both those with chronic kidney disease and those with liver disease.

Lactic acidosis occurs when lactic acid builds up in the blood and is caused by the body having to metabolize sugars without the presence of oxygen instead of aerobically. People not on Metformin may develop lactic acidosis from vigorous exercise, serious illness, injury, or drug toxicity.

Symptoms of lactic acidosis related to Metformin may be mild or severe and can include shortness of breath, swelling, weakness, and muscle pain. If you experience these symptoms while taking Metformin you should seek medical help right away. If lactic acidosis goes untreated, it may result in severe complications or even death (cardiac arrest.)

Metformin may result in a B12 deficiency, a complication which is known as "pernicious anemia" and can lead to permanent neurological damage. B12 deficiency is also linked with an increased risk of strokes. Early symptoms of B12 deficiency may include anemia, ringing in the ears, and depression. For those using metformin, it is important to have your B12 levels monitored so a lack of the vitamin can be addressed before a deficiency occurs.

Common Names

Metformin can go by several names, which is confusing for many people. Common names for Metformin include:

  • Fortamet
  • Glucophage
  • Glucophage XR
  • Glumetza
  • Riomet

Metformin can also be combined with other diabetes medicines. If you are unsure what you are taking or how your medicines work you should ask your healthcare provider:

  • Actoplus Met (containing Metformin, Pioglitazone)
  • Avandamet (containing Metformin, Rosiglitazone)
  • Glucovance (containing Metformin, Glyburide)
  • Invokamet (containing Metformin HCl/Canagliflozin)
  • Janumet (containing Metformin, Sitagliptin)
  • Janumet XR (containing Metformin, Sitagliptin)
  • Jentadueto (containing Metformin, Linagliptin)
  • Kazano (containing Metformin/Alogliptin)
  • Kombiglyze XR (containing Metformin, Saxagliptin)
  • Metaglip (containing Metformin, Glipizide)
  • Prandimet (containing Metformin, Repaglinide)
  • Synjardi (containing Metformin, Jardiance)
  • Xi Guo XR (containing Metformin HCl, Dapagliflozin)

A Word From Verywell

Metformin is an excellent choice of medication for people with type 2 diabetes and is recommended as the preferred medication beginning at the time of diagnosis for those who don't have any contraindications (reasons not to use the drug.) Based on its mechanism of action it is not effective for people with type I diabetes. Metformin works to reduce insulin resistance in addition to other mechanisms of action. In contrast to many diabetes medications, it does not cause weight gain and does not have the side effect of hypoglycemia, which can be very serious.

Side effects such as diarrhea and gas are common when beginning the medication, but can often be alleviated by carefully titrating the dose upward over a period of time. Less common but possibly serious side effects may include lactic acidosis and B12 deficiency. Knowing the possible symptoms of lactic acidosis and monitoring B12 can offset most serious complications.

While metformin is an excellent choice in addressing type 2 diabetes, lifestyle approaches such as a healthy diet and weight reduction (in those who are overweight) are the most important ways to address insulin resistance and avoid the possible long-term consequences of diabetes.

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