When Is the Best Time to Take Metformin: Morning or Night?

Metformin is a medication mainly prescribed to people with prediabetes and type 2 diabetes to help control blood sugar. If you've got a script for the drug, you may be wondering: When's the best time to take metformin? Morning or night?

The American Diabetes Association (ADA) confirms in a statement paper published February 2012 in ‌Diabetes Care‌ that it considers metformin a first-line medication for type 2 diabetes because it is highly effective and typically well-tolerated. And according to the Mayo Clinic, taking metformin at the right time of day is an important part of ensuring that the medication works correctly.

Here, we'll dig into how the drug works and the different dosages to help you decide whether you should take your dose in the morning or at night.

People with type 2 diabetes struggle with high blood glucose levels, aka high blood sugar. Glucose — the body's main source of fuel — comes from two sources: digestion of the carbohydrates in food, and the liver. The hormone insulin is responsible for moving glucose out of the bloodstream and into the cells, which use it for energy. Through this process, insulin lowers blood sugar levels.

But people with type 2 diabetes have cells that have become insensitive to insulin, and essentially ignore its effects. This is called insulin resistance. Metformin combats this by making the muscle cells more sensitive to insulin.

When the body isn't getting glucose from food, such as between meals or overnight, the liver makes sure the cells still have energy by releasing its own store of glucose, per the Diabetes Teaching Center at the University of California, San Francisco. Metformin plays a role here, too: It limits the liver's glucose production, as described by a study published in the November 2013 ‌Pharmacogenetics and Genomics‌.

Metformin comes in two varieties: standard and extended release. Standard metformin is typically taken two or three times per day, either as a pill or a liquid, according to the U.S. National Library of Medicine.

Metformin should always be taken with food to help reduce gastrointestinal (GI) side effects such as stomach pain or discomfort. Typically, it's best to take standard metformin both in the morning and in the evening, such as with the first and last meal of the day.

If you are taking a third dose, be sure to consult with your doctor about the best time to take it.

Metformin extended-release (ER), also listed by the U.S. National Library of Medicine as metformin hydrochloride or metformin HCL, is a once-a-day medication that can be taken as a pill or a liquid.

Metformin HCL is metabolized slowly, over 24 hours, which helps reduce GI side effects. Metformin ER is often a good option for people who experience adverse GI symptoms with standard metformin.

Metformin HCL should be taken at night, with food. Elizabeth Halprin, MD, clinical director of adult diabetes at Boston's Joslin Diabetes Center, explains why timing metformin HCL with the evening meal is so important. "In normal physiology, a person's liver often makes glucose overnight," she says. "So, it's not uncommon for a person to go to bed with a good blood glucose level and wake up with a higher one because their liver has been releasing sugar [all night]."

Metformin turns off or slows down this process, so it can be more effective at night in treating fasting high blood sugar.

According to the ADA, the most common adverse reactions to metformin involve the stomach and GI tract. These include:

• Diarrhea
• Nausea
• Vomiting
• Gas
• Abdominal pain

An ADA safety report published in the April 2012 issue of ‌Diabetes Care‌ found that these symptoms generally subside as the body adjusts to the medication.

According to the Mayo Clinic, patients will typically start taking standard metformin at the lowest dose, either metformin 500 milligram pills or 5 milliliter liquid.

Starting on the lowest dose gives the body a chance to adjust to the medication and reduces the risk of side effects. Once the body adjusts, the dose can be increased as needed.

Patients starting metformin HCL may start off with a higher dose. The maximum daily dose of standard metformin is usually not more than 2,500 milligrams, while the maximum dose of metformin extended-release is 2,000 milligrams.