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Metformin: 10 Things You Should Know

Medically reviewed on Apr 26, 2017 by L. Anderson, PharmD

Metformin is a Workhorse for Type 2 Diabetes

Metformin, also known by the brand names Glucophage, Glucophage XR, Fortamet, and others, has been available for the oral treatment of type 2 diabetes since 1995. Metformin helps to control blood sugar (glucose) levels and is sometimes used in combination with insulin or other medications.

Metformin is a true workhorse for diabetics: a study in JAMA Internal Medicine showed that people newly diagnosed with type 2 diabetes who were initially started on metformin were less likely to need other diabetic drug treatments to control their blood sugar. In fact, metformin is recommended in guidelines as the first-line drug treatment for new patients.

Metformin is Truly Lifesaving

We know that starting type 2 diabetes treatment with metformin helps to prevent the need for additional diabetes medications in the long-term. But what else does it do? A study from the Annals of Internal Medicine demonstrated that starting diabetes treatment with metformin is also linked with a lower long-term risk of heart attack, stroke, and death than starting with a sulfonylurea, like glyburide or glipizide.

However, researchers can't say whether the difference is due to extra risk from sulfonylurea drugs, added benefits from metformin, or both.

Diabetes is Expensive but Metformin is Affordable

A generic form of both regular-release and extended-release metformin is available at your pharmacy. However, prices will vary from city to city, and even pharmacy to pharmacy. There are several different strengths of metformin, too. It may be that instead of taking the 1,000 mg (1 gram) tablet of metformin per dose you could take two 500 mg tablets and save money. Always ask for the least costly version of generic metformin, as some generics may be more expensive.

If at any time you feel like you cannot afford your medications, have a frank discussion with your doctor or pharmacist to look at other options. Free samples, discount coupons, and even a switch to a more affordable drug class may be possible.

Insulin Resistance is the Culprit

There are many forces at work when a patient is diagnosed with type 2 diabetes. Insulin resistance is one of them, where the hormone insulin is not used effectively and too much sugar is left in the blood. Metformin works to make the body's cells more sensitive to insulin and decreases the amount of sugar naturally produced in the liver.

Guidelines published in the Annals of Internal Medicine also state that doctors should tailor blood sugar targets and treatments to the individual patient. While metformin is a recommended first-line therapy, some patients may need to be started on a second drug at the same time to reach blood sugar goals.

Can't You Smell That Smell?

Pharmacists and patients are well aware that metformin may come with a fishy smell when you open the bottle. The smell does not mean the drug is spoiled, it's just due to it's inherent characteristics. Metformin is associated with relatively few side effects, but nausea may be one of them, possibly due to this 'fishy' odor.

According to a report published in the Annals of Internal Medicine, some extended-release forms of metformin have a lower odor, and may be less likely to cause nausea. If you can't tolerate your metformin, let your doctor know. A switch to the extended-release form or a different manufacturer may do the trick.

Hypoglycemia: A Smaller Risk

Hypoglycemia, or excessively low blood sugar, can occur due to the use of many diabetes medications. One advantage of metformin is its low risk of causing hypoglycemia in only about 1% to 10% of patients. However, if someone has not eaten adequately, plays in strenuous sports without eating, or is also taking other other glucose-lowering agents such as sulfonylureas or insulin, hypoglycemia can set in.

Drinking alcohol with metformin can also lead to low blood sugar. Elderly or malnourished patients, and those with adrenal or pituitary insufficiency are especially at risk for low blood sugar.

Lactic Acidosis: A Rare Side Effect

A serious side effect called 'lactic acidosis' is listed in the patient education sheet for metformin. It's important you know about it, but it's also important you realize it's a very rare side effect. Lactic acidosis is a build-up of lactic acid in your blood due to low oxygen levels. Lactic acidosis can occur in people with severe kidney or liver disease, although experts say metformin can be used in mild to moderate kidney disease.

Lactic acidosis has been reported in about one in 33,000 patients taking metformin over one year. Although rare, if lactic acidosis does occur, it can be fatal in up to half the people who develop it.

What Are the Signs of Lactic Acidosis?

If you take metformin, have your electrolyte levels checked 1 to 2 weeks after starting treatment. Signs of lactic acidosis include:

  • Feeling very weak or tired
  • Unusual muscle pain
  • Trouble breathing
  • Stomach discomfort, nausea
  • Feeling cold
  • Feeling dizzy
  • Suddenly developing a slow or irregular heartbeat
If you notice any of these signs, stop taking metformin and call your doctor right away.

Will Metformin Help Me Lose Weight?

Many people with type 2 diabetes have insulin resistance and need to lose weight. Of course, for anyone, the best way to lose weight is gradually through a combination of a healthy diet and daily exercise. However, large studies have looked at weight loss in patients taking metformin. Weight loss is variable. In some studies, patients have lost from 4 to 6.5 pounds (lbs.), while in other studies, only about 2 lbs. have been lost.

In general, while metformin is a useful drug to control blood sugar in diabetes, weight loss due to metformin alone may not be enough. Patients should use an appropriate diet and regular exercise for weight control in type 2 diabetes.

How Should I Take Metformin?

Metformin comes in a regular-release and extended-release tablets in varying strengths. Metformin is usually taken with a meal. It may be taken twice a day, but some forms of metformin are taken only once daily.

Metformin can cause stomach upset, nausea or diarrhea at the beginning of treatment, but for many people these effects will subside over time. To help minimize these reactions and determine the most effective dose, your doctor will start you on a low dose and gradually increase it over time. In adults, the maximum daily dose of regular-release metformin is 2550 mg and the maximum daily dose of extended-release metformin is 2000 mg.

PCOS: An Off-Label Use for Metformin

Polycystic ovary syndrome (PCOS) is a disorder in which an imbalance of sex hormones can cause changes in the menstrual cycle, ovarian cysts, trouble getting pregnant, acne, facial hair growth, insulin resistance and other health problems. PCOS affects 5 to 15 percent of women of childbearing age, and they may have elevated diabetes risk and heart disease risk throughout life.

Metformin is one treatment used "off-label" to treat PCOS. Your doctor may prescribe diabetes medicines that reduce insulin resistance. Several medicines used to treat type 2 diabetes, including metformin (Glucophage), can decrease testosterone levels, restore normal menstrual cycles and restore fertility. Other medications, such as birth control pills or spironolactone may be used, too.

Finished: Metformin: 10 Things You Should Know

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  • Roumie C., Hung A., Greevy R., Grijalva C., Liu X., Murff H., Elasy T., Griffin M.; Comparative Effectiveness of Sulfonylurea and Metformin Monotherapy on Cardiovascular Events in Type 2 Diabetes Mellitus: A Cohort Study. Ann Intern Med. 2012;157:601-610. doi: 10.7326/0003-4819-157-9-201211060-00003. Accessed April 26, 2017
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  • Diabetes Prevention Program Research Group. Long-term safety, tolerability, and weight loss associated with metformin in the Diabetes Prevention Program Outcomes Study. Diabetes Care. 2012;35:731-737. Abstract. Accessed April 26, 2017.
  • Domecq J, Prutsky G, Leppin A, et al. Clinical review: Drugs commonly associated with weight change: a systematic review and meta-analysis. J Clin Endocrinol Metab. 2015;100:363-70. Accessed April 26, 2017 at http://www.ncbi.nlm.nih.gov/pubmed/25590213
  • Female Hormone Disorder Linked to Numerous Health Conditions. Drugs.com. Jan. 27, 2015. Accessed April 26, 2017 at https://www.drugs.com/news/female-hormone-disorder-linked-numerous-health-conditions-55404.html
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