metformin ER
Metformin extended-release (ER) is a prescription medication used along with a healthy diet and exercise to treat Type 2 diabetes. Unlike metformin immediate-release (IR) tablets, metformin ER is taken by mouth once daily. To minimize stomach-related side effects of this medication, such as diarrhea and nausea, it's best to take it with the evening meal. In some cases, people who take metformin ER might experience modest weight loss.
What is Metformin ER?
What is Metformin ER used for?
Type 2 diabetes in adults
How Metformin ER works
Metformin ER 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?
Common Side Effects
- Diarrhea (10%)
- Nausea and vomiting (7%)
Other Side Effects
- Belly pain
- Constipation
- Swollen belly
- Indigestion
- Excess gas
- Dizziness
- Headache
- Upper respiratory infection (e.g., cough, fever, sore throat)
- Changes in taste
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
Pros
Available as a lower-cost generic medication
Only taken once a day
Might cause less diarrhea than metformin immediate-release
Cons
Need to take with evening meal
Not safe for use in people with moderate-to-severe kidney disease
Not approved for people with Type 1 diabetes
Pharmacist tips for Metformin ER
Take metformin ER with your evening meal. Metformin ER can cause stomach problems, including diarrhea, nausea, vomiting, and belly pain. So food can help lower the risk of these side effects.
Swallow metformin ER tablets whole. Don't cut, crush, or chew the tablets. Doing so can affect how the medication gets absorbed.
It's normal to see what looks like a metformin ER tablet in your stool. This medication is still getting absorbed and you're seeing the protective coating.
You'll need to take metformin ER regularly to see a noticeable effect on your blood sugar. It might take up to 2 months to experience maximum benefit from this medication.
While you're taking metformin ER, 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 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 a provider or radiologist about your medication history before getting any procedures done. The contrast dyes that are used for certain imaging procedures can temporarily affect your kidneys. If you're taking metformin ER, this effect on the kidneys can raise your risk of metformin buildup in your body and lactic acidosis, which can be dangerous. Don't restart this medication until your provider checks your kidney health to make sure it's safe for you to do so.
If you feel cold in your hands or feet, dizzy, weak, confused, nauseous, or have trouble breathing, belly pain, or a racing heart, stop taking metformin ER and get medical attention right away. These can be signs of a serious condition called lactic acidosis (high acid levels in the blood), which sometimes can require treatment in the hospital.
Metformin ER can interact with certain medications. For example, ranolazine (Ranexa), a medication used to treat chest pain, can expose your body to more metformin, which raise your risk of side effects. Let your provider or pharmacist know what medications you're taking, including over-the-counter products and supplements, before you start metformin ER.
Make sure to get your routine blood tests done on time while you’re taking metformin ER. 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 (too much acid in your blood).
If you're taking metformin ER with other diabetes medications, like insulin or glipizide, you might be at risk of having low blood sugar. Make sure to check your blood sugar if you feel shaky, confused, or have a fast heartbeat. If you have low blood sugar (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 provider on a diet and exercise plan while taking metformin ER.
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Frequently asked questions about Metformin ER
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What are the risks and warnings for Metformin ER?
Metformin ER 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 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 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 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 provider will check your vitamin B12 levels through blood work every 2 to 3 years. If needed, your provider might recommend that you take vitamin B12 supplementation. Let your provider 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, you might be at higher risk for dangerously low blood sugar levels. Because of this, your 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 dosage forms
| Dosage | Quantity | Price as low as | Price per unit |
|---|---|---|---|
| 500mg | 30 tablets | $42.46 | $1.42 |
Typical dosing for Metformin ER
The typical starting dose is 500 mg by mouth once daily with the evening meal. Your provider might raise your dose every week if you need to lower your blood sugar more. The maximum dose is 2,000 mg once daily.
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Metformin ER contraindications
Severe kidney problems
Sudden or long-term acidosis (dangerously high levels of acid), including diabetic ketoacidosis
What are alternatives to Metformin ER?
What is the latest news about Metformin ER?
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References
Best studies we foundAmerican Diabetes Association. (2023). Standards of care in diabetes—2023 abridged for primary care providers. Clinical Diabetes.
American Kidney Fund. (2023). 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.
Quallent Pharmaceuticals Health LLC. (2023). Metformin ER 500 MG- metformin er 500 mg tablet; Metformin 750 MG- metformin er 750 mg tablet [package insert]. DailyMed.
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