Diabetes Medicine: Metformin

If you have diabetes, chances are you’re taking some type of medicine to help control it. If you have Type 1 diabetes, you must take insulin. But with Type 2 diabetes, there are many options, ranging from no medicine to diabetes pills to non-insulin injectables to insulin. While you may be able to manage your diabetes with healthy eating, weight control, and physical activity, there’s a high likelihood that at some point, you may need to take medication, including insulin. Unless your blood sugar and A1C levels are quite high, you would likely start on a type of diabetes pill. Today, there are nine classes of diabetes pills. Some are more commonly used (and more effective) than others:

• Metformin
• Sulfonylureas
• Meglitinides
• Thiazolidinediones (TZDs)
• DPP-4 inhibitors
• SGLT2 inhibitors
• Alpha-glucosidase inhibitors
• GLP-1 agonists
• Bile acid sequestrants

And to add to the mix, many of these medicines are available in combination form; for example, metformin can be combined with a sulfonylurea, a DPP-4 inhibitor, TZDs, or an SGLT2 inhibitor. Combination pills can save time and money and make pill-taking easier.

This week, we’ll focus on one of the most commonly prescribed diabetes pills: metformin.

What is metformin?
Metformin is a medicine in a class called biguanides. It lowers blood sugar levels by decreasing the amount of glucose released into the bloodstream by the liver. Metformin is also an “insulin sensitizer,” meaning that it works to make the cells in your body more receptive to insulin. When cells are insulin sensitive, they are able to take more glucose from the blood to be used for energy. Because metformin does not signal the pancreas to release insulin, there is little risk of low blood sugar (hypoglycemia) when taking this drug.

Metformin is available as a generic drug, but brand names include Glucophage, Glucophage XR, Glumetza, Riomet, and Fortamet.

How is metformin taken?
Metformin comes in tablet and liquid form. It also is available as an extended-release (long-acting) tablet. The regular tablet and the liquid are generally taken with meals one to three times each day. The extended-release form is typically taken once a day with the evening meal. Your doctor will likely start you off on a lower dose of metformin — say, 500–1,000 milligrams (mg) per day — and then gradually increase the dose. The maximum dose of metformin is usually not more than 2,000 mg per day.

What are the side effects of metformin?
Metformin is a very safe, effective, and generally well-tolerated medicine. For these reasons, many diabetes management guidelines recommend starting people with Type 2 diabetes on this medicine, even when a person is first diagnosed with diabetes. But, as with all medicines, it’s not free of side effects. The most common side effects include:

• Upset stomach
• Bloating
• Gas
• Diarrhea
• Decreased appetite
• Lower back or side pain
• Heartburn

Symptoms, if they occur at all, are less likely if your doctor starts you off on a lower dose and then gradually increases the dose to the prescribed amount. Also, take your metformin with food to help lower the risk of symptoms.

A more serious but rare side effect is called lactic acidosis. Lactic acidosis happens when there is not enough oxygen in the body and too much lactic acid builds up in the blood. Dehydration and drinking large amounts of alcohol can bring on lactic acidosis, but some medical conditions, like cancer, kidney failure, heart failure, HIV and AIDS, and respiratory problems can cause this, too. If you have any of these conditions and take metformin, you are at higher risk of getting lactic acidosis.

Lactic acidosis can be life threatening, so it’s important to be aware of the symptoms and seek medical help right away if you are experiencing them. Symptoms include:

• Muscle pain or weakness
• Numbness in the arms or legs
• Trouble breathing
• Stomach pain
• Feeling very weak or dizzy
• A slow or uneven heart rate
• Nausea with vomiting

What else should you know about metformin?
Metformin may decrease the absorption of vitamin B12, and this can put you at risk for B12 deficiency. If you’ve been taking metformin for several years and/or if you have numbness, pain, or tingling in your hands or feet, ask your doctor to check your blood vitamin B12 level. You may need to take a B12 supplement.

If you need an x-ray or CT scan that involves a dye being injected into your vein, you’ll need to temporarily stop taking metformin.

If you take the extended-release form of metformin, be sure to swallow it whole. Don’t crush, chew, or break the tablet.

Also, if you take the extended-release form, you may notice part of the tablet in your stool. This is normal and nothing to worry about. Your body has absorbed the medicine.

When first starting on metformin, you should notice an improvement in your blood sugar levels within a few weeks; however, it may take a few months to see its full effect. Be sure to check your blood sugar levels as instructed by your doctor so that you both can see how the medicine is working for you.