metformin ER
Metformin ER (Glumetza) is a biguanide. It's used to control blood sugar levels in adults with Type 2 diabetes. Metformin ER (Glumetza) is taken by mouth, typically once daily with an evening meal. Some of the more common side effects of this medication include diarrhea and nausea. But metformin ER (Glumetza) is less likely to cause stomach-related side effects than metformin immediate-release (IR) tablets. Metformin ER (Glumetza) is available as both brand-name and generic versions.
What is Metformin ER (Glumetza)?
What is Metformin ER (Glumetza) used for?
Type 2 diabetes in adults
How Metformin ER (Glumetza) works
Metformin ER (Glumetza) is a biguanide. It lowers the amount of sugar that your liver makes, as well as lowers the amount of sugar absorbed through the intestines. In addition, it also makes your body more sensitive to insulin. This means your cells are better able to take up sugar from the bloodstream and use it as energy.
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What are the side effects of Metformin ER (Glumetza)?
Common Side Effects
- Low blood sugar (dizziness, shaking; 14%)
- Diarrhea (13%)
- Nausea (7%)
Serious Side Effects
- Buildup of lactic acid: confusion, feeling weak, fast or slow heartbeat, rapid breathing, no appetite, nausea, vomiting
Source: DailyMed
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The following side effects have also been reported
Side effects that you should report to your care team as soon as possible:
- Allergic reactions—skin rash, itching, hives, swelling of the face, lips, tongue, or throat
- High lactic acid level—muscle pain or cramps, stomach pain, trouble breathing, general discomfort and fatigue
- Low vitamin B12 level—pain, tingling, or numbness in the hands or feet, muscle weakness, dizziness, confusion, trouble concentrating
Side effects that usually do not require medical attention (report these to your care team if they continue or are bothersome):
Pros and cons of Metformin ER (Glumetza)
Pros
Available as a lower-cost generic medication
Can take just once a day
Might cause less diarrhea than metformin immediate-release
Unlikely to cause weight gain, unlike other blood sugar medications
Cons
Can cause lactic acidosis (high acid levels in the blood)
Not safe for use in people with moderate-to-severe kidney disease
Not approved for people with Type 1 diabetes
Tablets must be swallowed whole
Pharmacist tips for Metformin ER (Glumetza)
Take metformin ER (Glumetza) with your evening meal. Metformin ER (Glumetza) can cause stomach problems, including diarrhea and nausea. So food can help lower the risk of these side effects.
Swallow metformin ER (Glumetza) tablets whole. Don't cut, crush, or chew the tablets. Doing so can affect how the medication gets absorbed.
You might see the shell of the metformin ER (Glumetza) tablet and a soft mass of the inactive ingredients in your stool. This isn't harmful and can be expected.
While you're taking metformin ER (Glumetza), make sure to drink enough fluids to keep hydrated, especially if you're experiencing vomiting or diarrhea or feeling ill. These conditions can lead to dehydration and raise your risk of having a buildup of lactic acid in your blood.
If you're scheduled for a surgery, let your primary care provider know ahead of time. They can discuss with you when to stop metformin ER (Glumetza) before surgery and when to restart this medication afterwards. This is because you might not be able to eat or drink during the time around your surgery, which can raise your risk of lactic acidosis.
Talk with your healthcare team about your medication history before getting any procedures done. The contrast dyes that are used for certain imaging procedures can temporarily affect your kidneys and raise your risk of metformin buildup in your body and lactic acidosis, which can be dangerous. Don't restart this medication until your primary care provider checks your kidney health to make sure it's safe for you to do so.
If you feel tired, weak, or have trouble breathing, stop taking metformin ER (Glumetza) and get medical attention right away. These might be signs of a serious side effect called lactic acidosis, which sometimes can require treatment in the hospital.
Metformin ER (Glumetza) can interact with certain medications. For example, ranolazine (Ranexa), a medication used to treat chest pain, can expose your body to more metformin, which raises your risk of side effects. Let your healthcare team know what medications you're taking, including over-the-counter products and supplements, before you start metformin ER (Glumetza).
Make sure to get your routine blood tests done on time while you’re taking metformin ER (Glumetza). By doing so, your provider can check for side effects, like liver injury or changes to your vitamin B12 levels, or your risk for lactic acidosis.
If you're taking metformin ER (Glumetza) with other diabetes medications, like insulin or glipizide, you might be at higher risk of having low blood sugar. Make sure to check your blood sugar if you feel shaky, confused, or have a fast heartbeat. If your blood sugar level is low (less than 70 mg/dL), know how to treat it and when you need to call 911.
It's important to eat healthy and exercise regularly to keep your blood sugar under control. Make sure to work with your healthcare team on a diet and exercise plan while taking metformin ER (Glumetza).
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What are the risks and warnings for Metformin ER (Glumetza)?
Metformin ER (Glumetza) can cause some serious health issues. This risk may be even higher for certain groups. If this worries you, talk to your doctor or pharmacist about other options.
Lactic acidosis (too much acid in your body)
Risk factors: Kidney or liver problems | Heart failure or heart attack | Age 65 or older | Not eating food or fasting before surgery | Excessive alcohol use | Imaging procedure using contrast dye | Taking certain medications that affect the kidneys
Metformin ER (Glumetza) can cause a rare, but serious medical condition called lactic acidosis (too much lactic acid in your blood). If left untreated, this condition can lead to other health problems, including organ failure, which can be deadly. Discuss with your primary care provider about your medical history before starting metformin ER (Glumetza) and any planned procedures during treatment. They can check for your risk for lactic acidosis. Get medical attention right away if you experience trouble breathing, irregular heartbeat, muscle pain, belly pain, or feeling very tired or dizzy. These can be signs that you have too much lactic acid in your blood.
Low vitamin B12 levels
Risk factors: Long-term use of metformin | Lower-than-average calcium or vitamin B12 intake or absorption
Taking metformin ER (Glumetza) for a long period of time can cause your vitamin B12 levels to drop. Having low vitamin B12 levels can lead to a higher risk of anemia. Your primary care provider will check your vitamin B12 levels through blood work every 2 to 3 years. If needed, they might recommend that you take vitamin B12 supplementation. Let your healthcare team know if you frequently have low energy, dizziness, muscle problems, or tingling or numbness in your hands and feet.
Risk of low blood sugar levels
If you're using insulin or taking another medication that raises insulin levels while taking metformin ER (Glumetza), you might be at higher risk for dangerously low blood sugar levels. Because of this, your primary care provider will likely need to adjust the doses of your blood sugar medications. Make sure you're familiar with symptoms of low blood sugar levels, such as shakiness, hunger, confusion. Keep glucose tablets or other fast-acting carbohydrates with you at all times so you can quickly treat hypoglycemia.
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Metformin ER (Glumetza) dosage forms
Typical dosing for Metformin ER (Glumetza)
The typical starting dose is 500 mg by mouth once daily with the evening meal. Your provider might raise the dose every 1 to 2 weeks, as needed. The maximum dose is 2,000 mg once daily.
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Metformin ER (Glumetza) contraindications
Severe kidney problems
Sudden or long-term acidosis (dangerously high levels of acid), including diabetic ketoacidosis
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References
Best studies we foundAgency for Toxic Substances and Disease Registry. (2023). ToxFAQs™ for n-Nitrosodimethylamine (NDMA).
American Diabetes Association. (2023). Standards of care in diabetes – 2023 abridged for primary care providers. Clinical Diabetes.
American Kidney Fund. (2024). Stages of kidney disease (CKD).
MedlinePlus. (2022). Lactic acidosis.
MedlinePlus. (2023). Dehydration.
National Heart, Lung, and Blood Institute. (2022). Vitamin B12–deficiency anemia.
Pala, L., et al. (2014). The "slower" the better. Journal of Endocrinological Investigation.
Sun Pharmaceutical Industries, Inc. (2024). Metformin hydrochloride tablet, film coated, extended release [package insert]. DailyMed.
U.S. Food and Drug Administration. (2020). Questions and answers: NDMA impurities in metformin products.
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