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Medical Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice.
Brand Name
Metformin
Generic Name
Metformin
Active Ingredient
MetforminCategory
Dipeptidyl Peptidase 4 Inhibitor [EPC]
Salt Form
Hydrochloride
Variants
4
Different strengths and dosage forms
| Strength | Form | Route | NDC |
|---|---|---|---|
| 500 mg/1 | TABLET, EXTENDED RELEASE | ORAL | 50742-633 |
| 1000 mg/1 | TABLET, EXTENDED RELEASE | ORAL | 67046-1584 |
| 1000 mg/1 | TABLET, EXTENDED RELEASE | ORAL |
References used for this content
This page is for informational purposes only and does not replace medical advice. Before using any prescription or over-the-counter medication for Metformin, you must consult a qualified healthcare professional.
| 500 mg/1 | TABLET, EXTENDED RELEASE | ORAL | 67046-1557 |
Detailed information about Metformin
Metformin is a biguanide antihyperglycemic agent used as first-line therapy for the management of type 2 diabetes mellitus. It works by reducing hepatic glucose production and improving insulin sensitivity without causing hypoglycemia.
For adults with type 2 diabetes, the dosage of Metformin must be individualized based on effectiveness and tolerance. Healthcare providers typically follow a 'start low and go slow' approach to minimize gastrointestinal upset.
Metformin is FDA-approved for pediatric patients aged 10 years and older.
Metformin is not currently recommended for children under the age of 10 due to a lack of clinical safety and efficacy data in this age group.
Because Metformin is cleared by the kidneys, dosage must be adjusted based on the Estimated Glomerular Filtration Rate (eGFR):
Metformin should generally be avoided in patients with clinical or laboratory evidence of hepatic (liver) disease. Liver impairment can significantly reduce the body's ability to clear lactate, increasing the risk of Metformin-associated lactic acidosis.
In patients over 65, Metformin should be used with caution. Because aging is associated with a natural decline in kidney function, healthcare providers will typically check renal function before starting the drug and periodically thereafter. The maximum dose is often kept lower in the geriatric population.
To get the most benefit from Metformin and reduce side effects, follow these guidelines:
If you miss a dose of Metformin, take it as soon as you remember with food. However, if it is almost time for your next scheduled dose, skip the missed dose and return to your regular dosing schedule. Do not double the dose to catch up, as this increases the risk of severe gastrointestinal distress and other complications.
An overdose of Metformin does not typically cause hypoglycemia but can lead to a life-threatening condition called Lactic Acidosis.
> Important: Follow your healthcare provider's dosing instructions precisely. Do not adjust your dose or stop the medication without medical guidance, as this can lead to dangerous spikes in blood sugar levels.
Gastrointestinal (GI) symptoms are the most frequent side effects associated with Metformin, occurring in up to 30% of patients. These are usually most severe when first starting the medication or after a dose increase.
Metformin is a highly effective medication, but it requires careful monitoring to ensure safety. The most critical aspect of Metformin safety is the maintenance of healthy kidney and liver function. Because the drug is excreted by the kidneys and lactate is processed by the liver, any impairment in these organs can lead to dangerous drug accumulation.
LACTIC ACIDOSIS: Post-marketing cases of Metformin-associated lactic acidosis have resulted in death, hypothermia, hypotension, and resistant bradyarrhythmias. The onset is often subtle, accompanied only by non-specific symptoms such as malaise, myalgia, respiratory distress, somnolence, and abdominal pain. Metformin-associated lactic acidosis is characterized by elevated blood lactate levels (>5 mmol/L), anion gap acidosis (without evidence of ketonuria or ketonemia), and an increased lactate/pyruvate ratio. If lactic acidosis is suspected, Metformin should be discontinued and the patient should be hospitalized immediately. Hemodialysis is recommended to correct the acidosis and remove the accumulated metformin.
While Metformin has few absolute contraindications regarding drug-drug interactions, certain combinations are avoided due to the extreme risk of renal failure or lactic acidosis:
There are specific clinical scenarios where Metformin must NEVER be used because the risks far outweigh any potential benefits:
Metformin is classified as Pregnancy Category B (under the older FDA system). Current data from large observational studies and randomized controlled trials have not shown an increased risk of major birth defects or miscarriage when Metformin is used during pregnancy.
Metformin is a biguanide that exerts its effects primarily by decreasing hepatic glucose production (gluconeogenesis) and increasing peripheral glucose uptake and utilization. At the cellular level, Metformin enters cells via organic cation transporters (OCTs). Once inside, it accumulates in the mitochondria. It inhibits Complex I of the mitochondrial respiratory chain, which leads to an increase in the AMP:ATP ratio. This energy stress activates AMP-activated protein kinase (AMPK).
Activated AMPK inhibits the expression of genes involved in gluconeogenesis (such as PEPCK and G6Pase) and activates the translocation of GLUT4 glucose transporters to the cell surface in muscle cells. Furthermore, Metformin antagonizes the action of glucagon by inhibiting adenylate cyclase, thereby reducing cyclic AMP (cAMP) levels and further suppressing glucose output from the liver.
Metformin lowers both fasting and postprandial (after-meal) plasma glucose. It does not cause insulin secretion and therefore does not cause hypoglycemia or hyperinsulinemia. A unique pharmacodynamic property of Metformin is its 'weight-neutral' or 'weight-loss' profile, which distinguishes it from sulfonylureas and insulin, which often cause weight gain. The onset of action is typically within 48 hours, but the full clinical effect on A1C levels may take 4 to 8 weeks of consistent dosing.
Common questions about Metformin
Metformin is primarily used to treat type 2 diabetes mellitus by helping to control blood sugar levels. It works by reducing the amount of glucose produced by the liver and improving the body's sensitivity to insulin. In addition to its FDA-approved use for diabetes, it is frequently prescribed off-label for Polycystic Ovary Syndrome (PCOS) to help regulate periods and improve fertility. It is also sometimes used in individuals with prediabetes to prevent the progression to full type 2 diabetes. Because it does not cause weight gain, it is a preferred choice for many patients and healthcare providers.
The most common side effects of Metformin are gastrointestinal in nature, including diarrhea, nausea, vomiting, gas, and abdominal discomfort. These symptoms occur in about one-third of patients, particularly when they first start the medication or increase their dose. Many people also report a temporary metallic taste in their mouth. To minimize these effects, it is highly recommended to take Metformin with a full meal and to start with a low dose that is gradually increased. For most patients, these side effects are mild and resolve on their own within a few weeks of consistent use.
Drinking alcohol while taking Metformin requires significant caution because alcohol can increase the risk of a rare but life-threatening condition called lactic acidosis. Both Metformin and alcohol can increase lactate levels in the blood, and when combined, they can overwhelm the liver's ability to clear these substances. While an occasional, small drink may be safe for some, binge drinking or chronic heavy alcohol use is strictly discouraged. It is important to discuss your alcohol consumption habits with your doctor to determine what is safe for your specific health profile. Always avoid alcohol if you have any history of liver or kidney problems.
Metformin is generally considered safe during pregnancy and is often used to treat gestational diabetes or to manage PCOS-related fertility issues. Extensive clinical data have not shown an increased risk of birth defects or miscarriages associated with Metformin use. However, insulin remains the traditional first-line treatment for diabetes during pregnancy in many clinical guidelines. Metformin does cross the placenta, so the decision to use it should be made in close consultation with an obstetrician or endocrinologist. They will weigh the benefits of stable blood sugar against any potential risks to the developing fetus.
Metformin begins to work within the first 48 hours of taking it, but its full glucose-lowering effects are not immediate. You may see a slight decrease in your blood sugar readings within a few days, but it typically takes 4 to 8 weeks of consistent use to see the full impact on your Hemoglobin A1C levels. Because the dose is usually started low and increased slowly to prevent stomach upset, it may take several weeks to reach your target maintenance dose. Patience and consistent monitoring of your blood sugar levels are key during the first two months of therapy.
You should never stop taking Metformin suddenly without first consulting your healthcare provider. Metformin is a long-term maintenance medication, and stopping it abruptly will likely cause your blood sugar levels to rise significantly. This can increase your risk of long-term diabetes complications such as vision loss, kidney damage, and nerve pain. If you are experiencing bothersome side effects, your doctor can help you lower the dose gradually or switch you to an extended-release version, which is often better tolerated. Always have a plan for an alternative treatment before discontinuing Metformin.
If you miss a dose of Metformin, you should take it as soon as you remember, provided you can take it with food. However, if it is almost time for your next scheduled dose, you should skip the missed dose and simply take your next dose at the regular time. Never take two doses at once to make up for a missed one, as this significantly increases the risk of severe nausea, diarrhea, and abdominal pain. Keeping your medication in a pill organizer or setting a daily alarm can help you stay consistent with your dosing schedule.
Unlike many other medications used to treat type 2 diabetes, such as insulin or sulfonylureas, Metformin does not cause weight gain. In fact, many patients experience modest weight loss when taking Metformin, typically ranging from 2 to 6 pounds. This weight loss is thought to be due to a combination of reduced appetite and the medication's effects on how the body stores and uses energy. Because of this 'weight-neutral' or 'weight-negative' profile, Metformin is often the preferred first-line treatment for patients with diabetes who are also overweight or obese.
Metformin is frequently taken in combination with other medications, but some interactions require careful monitoring. It is often combined with other diabetes drugs like Januvia (sitagliptin) or Jardiance (empagliflozin) to achieve better blood sugar control. However, certain drugs like cimetidine, dolutegravir, and specific diuretics can increase the levels of Metformin in your blood, potentially leading to more side effects. It is vital to provide your doctor and pharmacist with a complete list of all prescriptions, over-the-counter drugs, and herbal supplements you are taking to ensure there are no dangerous interactions.
Yes, Metformin is widely available as a very affordable generic medication in both immediate-release and extended-release formulations. The generic versions are bioequivalent to the brand-name versions (like Glucophage or Glucophage XR), meaning they have the same active ingredient and work the same way in the body. Because it has been on the market for decades, the generic versions are highly cost-effective and are covered by almost all insurance plans. Using the generic version is an excellent way to manage the costs of long-term diabetes care without sacrificing the quality of treatment.
Other drugs with the same active ingredient (Metformin)
> Warning: Stop taking Metformin and call your doctor immediately if you experience any of the following symptoms, which may indicate a medical emergency.
The primary long-term concern with Metformin is Vitamin B12 malabsorption. According to studies, up to 10-30% of patients on chronic Metformin therapy show evidence of reduced B12 absorption. If left untreated, this can cause permanent nerve damage or anemia. Patients are encouraged to discuss B12 supplementation with their doctor. Additionally, some evidence suggests that long-term Metformin use may have protective effects against certain cancers and cardiovascular disease, though these are currently areas of active research.
Metformin carries an FDA Black Box Warning for Lactic Acidosis. This is the most serious potential complication.
Report any unusual symptoms to your healthcare provider. Side effects are often manageable with dose adjustments or by switching to the extended-release (ER) version of the medication.
To ensure Metformin remains safe and effective, your healthcare provider will order regular laboratory tests:
Metformin alone does not usually cause drowsiness or impair your ability to drive. However, if you are taking Metformin in combination with other diabetes medications (like insulin), you may experience hypoglycemia (low blood sugar), which can cause dizziness, blurred vision, and impaired concentration. Always check your blood sugar before driving if you are on combination therapy.
Alcohol increases the risk of Metformin-associated lactic acidosis because it inhibits the liver's ability to clear lactate. While a small, occasional drink may be permissible for some, 'binge drinking' or chronic heavy use is dangerous. Discuss your alcohol consumption habits honestly with your doctor.
Do not stop taking Metformin suddenly without consulting your doctor. Stopping the medication will likely cause your blood sugar levels to rise, increasing the risk of long-term diabetes complications (such as nerve damage or kidney disease). If you need to stop Metformin due to side effects, your doctor will help you transition to an alternative therapy.
> Important: Discuss all your medical conditions, including history of heart, liver, or kidney disease, with your healthcare provider before starting Metformin.
For each major interaction, the mechanism usually involves the Organic Cation Transporters (OCT1, OCT2) or Multidrug and Toxin Extrusion (MATE) proteins. When these transporters are inhibited by other drugs, Metformin cannot be properly excreted, leading to increased toxicity. Conversely, drugs like steroids that increase blood sugar work through a pharmacodynamic interaction, opposing the therapeutic goal of Metformin.
> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking. Keep a current list and share it with every healthcare provider you visit.
These are conditions where Metformin might be used, but only with extreme caution and frequent monitoring:
There is no known cross-sensitivity between Metformin and other classes of diabetes medications (such as sulfonylureas or SGLT2 inhibitors). However, patients who have had reactions to other biguanides (like the now-withdrawn Phenformin) should not take Metformin.
> Important: Your healthcare provider will evaluate your complete medical history, including recent lab results, before prescribing Metformin to ensure you do not have any underlying contraindications.
Metformin is excreted into human breast milk in very small amounts. The concentration in milk is generally less than 1% of the mother's weight-adjusted dose. Studies have shown no adverse effects on the breastfed infant's growth or development. Metformin is considered compatible with breastfeeding by the American Academy of Pediatrics. However, healthcare providers should monitor the infant for any signs of gastrointestinal distress or unusual lethargy.
Metformin is approved for children and adolescents aged 10 to 16 years with type 2 diabetes.
In patients 65 and older, the primary concern is the age-related decline in kidney function.
As the kidneys are the sole route of Metformin elimination, renal status dictates the entire treatment plan.
Metformin should be avoided in patients with significant liver disease (e.g., Child-Pugh Class B or C). The liver's inability to clear lactate increases the risk of Metformin-associated lactic acidosis (MALA) exponentially. In patients with mild fatty liver (NAFLD), Metformin is often safe and may even be beneficial, but this must be determined by a specialist.
> Important: Special populations require individualized medical assessment. Always inform your doctor if you are pregnant, planning to become pregnant, or have any degree of kidney or liver disease.
| Parameter | Value |
|---|---|
| Bioavailability | 50% to 60% (Fasting) |
| Protein Binding | 0% (Negligible) |
| Half-life (t½) | 6.2 hours (Plasma); 17.6 hours (Blood) |
| Tmax | 2.5 hours (IR); 7 hours (ER) |
| Metabolism | None (Not metabolized by liver) |
| Excretion | Renal (90% unchanged in urine) |
Metformin is the only drug in the Biguanide class currently available in most markets. While it is often grouped with other oral antidiabetics, its mechanism is distinct from Sulfonylureas (which close K+ channels), SGLT2 inhibitors (which block glucose reabsorption in the kidney), and DPP-4 inhibitors (which increase incretin levels). Its unique ability to target the liver makes it the ideal 'foundation' therapy for type 2 diabetes management.