7 Metformin Side Effects, Plus FAQs About Long-Term Use
Metformin is used to manage and treat prediabetes, Type 2 diabetes, PCOS, and more. Learn about the common side effects and risks that come with metformin.
metformin ER (Fortamet)
Used for Diabetes Type 2
Used for Diabetes Type 2
Metformin ER (Fortamet) is a prescription medication used along with diet and exercise to treat Type 2 diabetes in adults. Compared to other types of metformin, metformin ER (Fortamet) uses an osmotic release system that lets the medication release slowly over time. It's typically taken by mouth once a day. To minimize stomach-related side effects, like diarrhea and nausea, it's best to take it with the evening meal. In some cases, people might experience modest weight loss. The brand-name version, Fortamet, is no longer available, but the generic version is still available.
What is Metformin ER (Fortamet)?
What is Metformin ER (Fortamet) used for?
- Type 2 diabetes in adults
How Metformin ER (Fortamet) works
Metformin ER (Fortamet) is a biguanide. It reduces the amount of sugar your liver makes and the amount absorbed through the gut. It also helps your body respond better to insulin, so your cells can take up sugar from the blood and use it for energy.
Drug facts
| Common Brands | Fortamet |
|---|---|
| Drug Class | Biguanide |
| Controlled Substance Classification | Not a controlled medication |
| Generic Status | Lower-cost generic available |
| Availability | Prescription only |
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Side effects of Metformin ER (Fortamet)
The following side effects may get better over time as your body gets used to the medication. Let your healthcare provider know immediately if you continue to experience these symptoms or if they worsen over time.
Common Side Effects
- Diarrhea (10%)
- Nausea (7%)
- Vomiting (7%)
Less Common Side Effects
- Stomach pain
- Constipation
- Swollen stomach
- Heartburn
- Passing gas
- Dizziness
- Headache
- Upper respiratory tract infection
- Changes in taste
Metformin ER (Fortamet) serious side effects
Contact your healthcare provider immediately if you experience any of the following.
- Lactic acidosis (buildup of lactic acid): confusion, feeling weak, fast or slow heartbeat, rapid breathing, reduced appetite, nausea, vomiting
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The following Metformin ER (Fortamet) 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):
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Pros and cons of Metformin ER (Fortamet)
Pros
- Usually only taken once a day
- Might cause less diarrhea than metformin IR
- Unlikely to cause weight gain, unlike other blood sugar medications
Cons
- Need to take with evening meal
- Not safe for use in people with moderate-to-severe kidney problems
- Tablets are typically large and need to be swallowed whole
Pharmacist tips for Metformin ER (Fortamet)
- Take metformin ER (Fortamet) with your evening meal. Metformin ER (Fortamet) 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 (Fortamet) tablets whole. Don't cut, crush, or chew the tablets. Doing so can affect how the medication gets absorbed in your body.
- You might see something in your stool that looks like a metformin ER (Fortamet) tablet. This is normal, harmless, and doesn’t affect how the tablets work.
- 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 (Fortamet) and get medical attention right away. These can be signs of a serious condition called lactic acidosis, which sometimes can require treatment in the hospital.
- While you're taking metformin ER (Fortamet), be sure to drink enough fluids to keep hydrated, especially if you're experiencing vomiting or diarrhea. These conditions can lead to dehydration and raise your risk for lactic acidosis.
- Metformin ER (Fortamet) can interact with certain medications. Let your healthcare team know what medications you're taking, including over-the-counter products and supplements, before you start metformin ER (Fortamet).
- Make sure to get your routine blood tests done on time while you’re taking metformin ER (Fortamet). This helps your healthcare team check for side effects, like liver injury, changes in your vitamin B12 levels, or your risk of lactic acidosis.
- If you're taking metformin ER (Fortamet) 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 it's low (under 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. Work with your healthcare team on a diet and exercise plan while taking metformin ER (Fortamet).
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Risks and warnings for Metformin ER (Fortamet)
Metformin ER (Fortamet) 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 (Fortamet) 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 healthcare team about your medical history before starting metformin ER (Fortamet) 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 (Fortamet) 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 healthcare team 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 care 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 (Fortamet), you might be at higher risk for dangerously low blood sugar levels. Because of this, your healthcare team 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 (Fortamet) dosage
The average cost for 60 tablets of 1000mg of Metformin ER (Fortamet) is $25.71 with a free GoodRx coupon. This is 97.82% off the average retail price of $1,181.30. 
Tablet
Tablet| Dosage | Quantity | Price as low as | Price per unit |
|---|---|---|---|
| 1000mg | 60 tablets | $25.71 | $0.43 |
| 500mg | 90 tablets | $24.04 | $0.27 |
Typical dosage for Metformin ER (Fortamet)
The typical starting dose is 500 mg by mouth once daily with the evening meal. Your healthcare team might raise your dose each week if you need more help lowering your blood sugar. The maximum dose is 2,000 mg once daily.
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How much does Metformin ER (Fortamet) cost?
To access savings, use a GoodRx coupon and pay just a fraction of the retail price.
Metformin ER (Fortamet) (generic)
$24.04
Metformin ER (Fortamet) contraindications
Contraindications are specific health conditions or situations in which a person should not take a medication due to safety concerns. If you have any of the following conditions or if any of the following apply to you, let your healthcare provider know because Metformin ER (Fortamet) will not be safe for you to take.
- Severe kidney problems
- Sudden or long-term acidosis (dangerously high levels of acid), including diabetic ketoacidosis
What are alternatives to Metformin ER (Fortamet)?
There are a number of medications that your doctor can prescribe in place of Metformin ER (Fortamet). Compare a few possible alternatives below.
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