Glucophage 850mg Tablets
WARNING: Rarely, metformin may cause too much lactic acid in the blood (lactic acidosis). The risk is higher in people who have kidney problems, liver problems, heart failure, use alcohol, or take certain other drugs, including topiramate. The risk is also higher in people who are 65 or older and in people who are having surgery, an exam or test with contrast, or other procedures. If lactic acidosis happens, it can lead to other health problems and can be deadly. Kidney tests may be done while taking this drug.Do not take this drug if you have a very bad infection, low oxygen, or a lot of fluid loss (dehydration).Call your doctor right away if you have signs of too much lactic acid in the blood (lactic acidosis) like confusion; fast breathing; fast or slow heartbeat; a heartbeat that does not feel normal; very bad stomach pain, upset stomach, or throwing up; feeling very sleepy; shortness of breath; feeling very tired or weak; very bad dizziness; feeling cold; or muscle pain or cramps. @ COMMON USES: It is used to lower blood sugar in patients with high blood sugar (diabetes).
Drug Class
Antidiabetic
Pharmacologic Class
Biguanide
Pregnancy Category
Not available
FDA Approved
Dec 1994
DEA Schedule
Not Controlled
Overview
What is this medicine?
Metformin is a medication used to help control blood sugar levels in people with type 2 diabetes. It works by reducing the amount of sugar your liver makes, decreasing the amount of sugar your body absorbs from food, and making your body more sensitive to insulin. It's often the first medicine prescribed for type 2 diabetes.
How to Use This Medicine
Taking Your Medication
To use this medication correctly, follow your doctor's instructions and read all the information provided. Take this medication with meals as directed. Continue taking the medication as prescribed by your doctor or healthcare provider, even if you start to feel better.
Storing and Disposing of Your Medication
Store this medication at room temperature, away from light and moisture. Avoid storing it in a bathroom. Keep all medications in a safe and secure location, out of the reach of children and pets.
Missing a Dose
If you miss a dose, skip it and take the next dose at your regular scheduled time, unless your doctor advises you to do otherwise. Do not take two doses at the same time or take extra doses to make up for the missed one.
To use this medication correctly, follow your doctor's instructions and read all the information provided. Take this medication with meals as directed. Continue taking the medication as prescribed by your doctor or healthcare provider, even if you start to feel better.
Storing and Disposing of Your Medication
Store this medication at room temperature, away from light and moisture. Avoid storing it in a bathroom. Keep all medications in a safe and secure location, out of the reach of children and pets.
Missing a Dose
If you miss a dose, skip it and take the next dose at your regular scheduled time, unless your doctor advises you to do otherwise. Do not take two doses at the same time or take extra doses to make up for the missed one.
Lifestyle & Tips
- Take metformin with meals to reduce stomach upset.
- Follow a healthy diet plan as recommended by your doctor or dietitian.
- Engage in regular physical activity as advised by your healthcare provider.
- Limit alcohol intake, as excessive alcohol can increase the risk of a serious side effect called lactic acidosis.
- Stay well-hydrated, especially during exercise or in hot weather.
Available Forms & Alternatives
Available Strengths:
Generic Alternatives:
Dosing & Administration
Adult Dosing
Standard Dose:
Initial: 500 mg twice daily or 850 mg once daily with meals. Titrate gradually. Maintenance: 850 mg twice daily or 1000 mg twice daily.
Dose Range:
500 - 2550 mg
Condition-Specific Dosing:
Type 2 Diabetes Mellitus:
Initial: 500 mg twice daily or 850 mg once daily with meals. Increase by 500 mg weekly or 850 mg every 2 weeks as tolerated. Max: 2550 mg/day (850 mg three times daily) or 2000 mg/day (extended-release).
Pediatric Dosing
Neonatal:
Not established
Infant:
Not established
Child:
Not established for <10 years. For 10-16 years: Initial 500 mg twice daily. Max 2000 mg/day.
Adolescent:
Initial 500 mg twice daily. Max 2000 mg/day.
Dose Adjustments
Renal Impairment:
Mild:
eGFR 60-89 mL/min/1.73m²: No dose adjustment needed. Monitor eGFR annually.
Moderate:
eGFR 45-59 mL/min/1.73m²: Assess benefits/risks of continuing. If continued, max dose 1000 mg/day. Monitor eGFR every 3-6 months. eGFR 30-44 mL/min/1.73m²: Not recommended to initiate. If already on metformin, reduce dose by 50% (max 1000 mg/day) and monitor eGFR every 3 months.
Severe:
eGFR <30 mL/min/1.73m²: Contraindicated.
Dialysis:
Contraindicated in patients with end-stage renal disease or on dialysis due to increased risk of lactic acidosis.
Hepatic Impairment:
Mild:
Not available
Moderate:
Not available
Severe:
Contraindicated in severe hepatic impairment due to increased risk of lactic acidosis.
Pharmacology
Mechanism of Action
Metformin is a biguanide that decreases hepatic glucose production, decreases intestinal absorption of glucose, and improves insulin sensitivity by increasing peripheral glucose uptake and utilization. It does not stimulate insulin secretion and therefore does not cause hypoglycemia when used alone.
Pharmacokinetics
Absorption:
Bioavailability:
50-60%
Tmax:
2-2.5 hours (immediate-release)
FoodEffect:
Food decreases the extent and slightly delays the absorption of metformin.
Distribution:
Vd:
654 L
ProteinBinding:
<5%
CnssPenetration:
Limited
Elimination:
HalfLife:
4-9 hours (plasma); 17.6 hours (blood)
Clearance:
Renal clearance is approximately 3.5 times greater than creatinine clearance, indicating tubular secretion.
ExcretionRoute:
Renal
Unchanged:
>90%
Pharmacodynamics
OnsetOfAction:
Days to weeks for full glucose-lowering effect
PeakEffect:
Typically within 2-3 weeks of reaching a stable dose
DurationOfAction:
Approximately 12 hours (immediate-release)
Safety & Warnings
BLACK BOX WARNING
Postmarketing cases of metformin-associated lactic acidosis have resulted in death, hypothermia, hypotension, and resistant bradyarrhythmias. The onset of metformin-associated lactic acidosis is often subtle, accompanied only by nonspecific symptoms such as malaise, myalgias, respiratory distress, somnolence, and abdominal distress. Metformin-associated lactic acidosis was characterized by elevated blood lactate levels (>5 mmol/L), anion gap acidosis (without evidence of ketonuria or ketonemia), and an increased lactate/pyruvate ratio; metformin plasma levels generally >5 mcg/mL. If metformin-associated lactic acidosis is suspected, discontinue GLUCOPHAGE immediately and institute general supportive measures in a hospital setting. Prompt hemodialysis is recommended.
Side Effects
Urgent Side Effects: Seek Medical Help Right Away
While rare, some people may experience severe and potentially life-threatening side effects when taking this medication. If you notice any of the following symptoms, contact your doctor or seek immediate medical attention:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Stomach problems that occur later during treatment, which may be a sign of lactic acidosis (an acid health problem in the blood)
Low blood sugar, which may be more likely when this medication is used with other diabetes medications. Symptoms may include:
+ Dizziness
+ Headache
+ Feeling sleepy or weak
+ Shaking
+ Fast heartbeat
+ Confusion
+ Hunger
+ Sweating
If you experience low blood sugar, follow your doctor's instructions for treatment, which may include taking glucose tablets, liquid glucose, or some fruit juices.
Other Possible Side Effects
Like all medications, this drug can cause side effects. While many people may not experience any side effects or only minor ones, it's essential to discuss any concerns with your doctor. Contact your doctor or seek medical help if you experience any of the following side effects or if they bother you or do not go away:
Stomach pain or heartburn
Gas
Diarrhea, upset stomach, or vomiting
Feeling tired or weak
Headache
This is not an exhaustive list of possible side effects. If you have questions or concerns about side effects, consult your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
While rare, some people may experience severe and potentially life-threatening side effects when taking this medication. If you notice any of the following symptoms, contact your doctor or seek immediate medical attention:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Stomach problems that occur later during treatment, which may be a sign of lactic acidosis (an acid health problem in the blood)
Low blood sugar, which may be more likely when this medication is used with other diabetes medications. Symptoms may include:
+ Dizziness
+ Headache
+ Feeling sleepy or weak
+ Shaking
+ Fast heartbeat
+ Confusion
+ Hunger
+ Sweating
If you experience low blood sugar, follow your doctor's instructions for treatment, which may include taking glucose tablets, liquid glucose, or some fruit juices.
Other Possible Side Effects
Like all medications, this drug can cause side effects. While many people may not experience any side effects or only minor ones, it's essential to discuss any concerns with your doctor. Contact your doctor or seek medical help if you experience any of the following side effects or if they bother you or do not go away:
Stomach pain or heartburn
Gas
Diarrhea, upset stomach, or vomiting
Feeling tired or weak
Headache
This is not an exhaustive list of possible side effects. If you have questions or concerns about side effects, consult your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
Seek Immediate Medical Attention If You Experience:
- Symptoms of lactic acidosis: unusual muscle pain, trouble breathing, unusual sleepiness, stomach pain, nausea, vomiting, dizziness, lightheadedness, slow or irregular heartbeat, feeling cold.
- Symptoms of low blood sugar (hypoglycemia) if taken with other diabetes medications: sweating, shaking, fast heartbeat, hunger, blurred vision, dizziness, tingling hands/feet.
- Signs of vitamin B12 deficiency: unusual tiredness, weakness, numbness or tingling in hands/feet.
Before Using This Medicine
Before Taking This Medication: Important Information to Share with Your Doctor
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Be sure to describe the allergic reaction you experienced, including any symptoms that occurred.
Certain health conditions, including:
+ Acidic blood problems
+ Kidney disease
+ Liver disease
Recent medical events, such as a heart attack or stroke
Any difficulties with eating or drinking, including situations where you may be required to fast before a procedure or surgery
* Upcoming or recent exams or tests that involve contrast agents, specifically within the past 48 hours
This list is not exhaustive, and it is crucial to discuss all your medications (prescription, over-the-counter, natural products, and vitamins) and health problems with your doctor and pharmacist. They will help determine if it is safe to take this medication in conjunction with your other treatments and health conditions. Never start, stop, or adjust the dosage of any medication without first consulting your doctor.
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Be sure to describe the allergic reaction you experienced, including any symptoms that occurred.
Certain health conditions, including:
+ Acidic blood problems
+ Kidney disease
+ Liver disease
Recent medical events, such as a heart attack or stroke
Any difficulties with eating or drinking, including situations where you may be required to fast before a procedure or surgery
* Upcoming or recent exams or tests that involve contrast agents, specifically within the past 48 hours
This list is not exhaustive, and it is crucial to discuss all your medications (prescription, over-the-counter, natural products, and vitamins) and health problems with your doctor and pharmacist. They will help determine if it is safe to take this medication in conjunction with your other treatments and health conditions. Never start, stop, or adjust the dosage of any medication without first consulting your doctor.
Precautions & Cautions
It is essential to inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication. Before consuming alcohol, discuss the potential risks with your doctor.
If you experience low blood sugar, do not operate a vehicle, as this can increase your risk of being involved in an accident. Monitor your blood sugar levels as instructed by your doctor. Additionally, have your blood work checked as directed by your doctor and discuss the results with them.
Be aware that stress, such as fever, infection, injury, or surgery, can affect your blood sugar control. Changes in physical activity, exercise, or diet can also impact your blood sugar levels. Adhere to the diet and exercise plan recommended by your doctor to maintain optimal blood sugar control.
If you experience diarrhea or vomiting, contact your doctor promptly, as you may need to increase your fluid intake to prevent excessive fluid loss. In hot weather or during physical activity, be cautious and drink plenty of fluids to avoid dehydration.
Long-term treatment with metformin may lead to decreased vitamin B-12 levels. If you have a history of low vitamin B-12 levels, consult with your doctor. Individuals 65 years or older should use this medication with caution, as they may be more susceptible to side effects.
Women of childbearing age who have not been ovulating may be at risk of pregnancy while taking this medication. If you wish to avoid pregnancy, use birth control measures while taking this drug. If you are pregnant, plan to become pregnant, or are breastfeeding, inform your doctor to discuss the potential benefits and risks to you and your baby.
If you experience low blood sugar, do not operate a vehicle, as this can increase your risk of being involved in an accident. Monitor your blood sugar levels as instructed by your doctor. Additionally, have your blood work checked as directed by your doctor and discuss the results with them.
Be aware that stress, such as fever, infection, injury, or surgery, can affect your blood sugar control. Changes in physical activity, exercise, or diet can also impact your blood sugar levels. Adhere to the diet and exercise plan recommended by your doctor to maintain optimal blood sugar control.
If you experience diarrhea or vomiting, contact your doctor promptly, as you may need to increase your fluid intake to prevent excessive fluid loss. In hot weather or during physical activity, be cautious and drink plenty of fluids to avoid dehydration.
Long-term treatment with metformin may lead to decreased vitamin B-12 levels. If you have a history of low vitamin B-12 levels, consult with your doctor. Individuals 65 years or older should use this medication with caution, as they may be more susceptible to side effects.
Women of childbearing age who have not been ovulating may be at risk of pregnancy while taking this medication. If you wish to avoid pregnancy, use birth control measures while taking this drug. If you are pregnant, plan to become pregnant, or are breastfeeding, inform your doctor to discuss the potential benefits and risks to you and your baby.
Overdose Information
Overdose Symptoms:
- Lactic acidosis (severe metabolic acidosis with elevated lactate levels)
- Hypoglycemia (if co-administered with sulfonylureas or insulin)
- Severe gastrointestinal upset (nausea, vomiting, diarrhea)
What to Do:
Call 1-800-222-1222 (Poison Control). Seek immediate medical attention. Hemodialysis is the most effective method to remove lactate and metformin from the blood.
Drug Interactions
Contraindicated Interactions
- Iodinated contrast agents (temporarily discontinue metformin at the time of or prior to the procedure and withhold for 48 hours after, and restart only after renal function has been re-evaluated and found to be normal)
- Alcohol (excessive acute or chronic intake due to increased risk of lactic acidosis)
- Drugs that increase risk of lactic acidosis (e.g., topiramate, zonisamide, acetazolamide, dichlorphenamide - carbonic anhydrase inhibitors)
Major Interactions
- Cimetidine (increases metformin plasma concentration by decreasing renal tubular secretion)
- Carbonic anhydrase inhibitors (e.g., topiramate, zonisamide, acetazolamide, dichlorphenamide - may increase risk of lactic acidosis)
- Drugs that impair renal function (e.g., NSAIDs, ACE inhibitors, ARBs, diuretics - may increase risk of lactic acidosis by reducing metformin clearance)
Moderate Interactions
- Cationic drugs eliminated by renal tubular secretion (e.g., amiloride, digoxin, morphine, procainamide, quinidine, ranitidine, triamterene, trimethoprim, vancomycin - may compete for renal tubular transport systems, potentially increasing metformin levels)
- Nifedipine (increases metformin absorption and excretion)
- Furosemide (increases metformin plasma and blood concentrations, but metformin decreases furosemide half-life)
- Glucocorticoids, sympathomimetics, diuretics, thyroid products, phenothiazines, oral contraceptives, niacin, calcium channel blockers, isoniazid (may cause hyperglycemia, requiring dose adjustment of metformin)
Minor Interactions
- Not available
Monitoring
Baseline Monitoring
Renal function (eGFR)
Rationale: To assess baseline kidney function and determine appropriate dosing or contraindication.
Timing: Prior to initiation of therapy.
HbA1c
Rationale: To establish baseline glycemic control.
Timing: Prior to initiation of therapy.
Vitamin B12 levels
Rationale: Metformin can decrease vitamin B12 levels.
Timing: Consider baseline measurement, especially in patients at risk for deficiency.
Routine Monitoring
HbA1c
Frequency: Every 3-6 months
Target: <7% (individualized)
Action Threshold: >7% (or individualized target) may require dose adjustment or additional therapy.
Renal function (eGFR)
Frequency: At least annually; more frequently (e.g., every 3-6 months) in elderly, debilitated, or patients with risk factors for renal impairment.
Target: >60 mL/min/1.73m²
Action Threshold: <45 mL/min/1.73m² requires dose adjustment or discontinuation; <30 mL/min/1.73m² is a contraindication.
Vitamin B12 levels
Frequency: Periodically, especially if anemia or neuropathy is suspected.
Target: Normal range
Action Threshold: Low levels may require supplementation.
Symptom Monitoring
- Symptoms of lactic acidosis: malaise, myalgia, unusual somnolence, respiratory distress, abdominal distress, increased gastric upset, dizziness, lightheadedness, hypothermia, bradyarrhythmias.
- Symptoms of hypoglycemia (if used in combination with insulin or sulfonylureas): sweating, tremor, hunger, confusion, irritability.
- Gastrointestinal side effects: nausea, vomiting, diarrhea, abdominal discomfort, metallic taste.
Special Patient Groups
Pregnancy
Metformin is generally considered safe and effective for use during pregnancy for gestational diabetes or pre-existing type 2 diabetes, especially when diet and exercise are insufficient. It is often continued throughout pregnancy if needed.
Trimester-Specific Risks:
First Trimester:
No increased risk of congenital malformations observed.
Second Trimester:
Generally considered safe and effective.
Third Trimester:
Generally considered safe and effective.
Lactation
Metformin is excreted into breast milk in small amounts. It is generally considered compatible with breastfeeding, and adverse effects on breastfed infants are not expected.
Infant Risk:
Low risk
Pediatric Use
Approved for use in children 10 years of age and older with type 2 diabetes. Dosing should be carefully titrated, and renal function monitored.
Geriatric Use
Use with caution in elderly patients due to the increased likelihood of decreased renal function. Renal function should be assessed more frequently in this population. The maximum dose may need to be lower.
Clinical Information
Clinical Pearls
- Metformin is the first-line pharmacologic agent for type 2 diabetes, especially in overweight or obese patients, due to its efficacy, low risk of hypoglycemia, and potential for weight neutrality or modest weight loss.
- Gastrointestinal side effects (nausea, diarrhea, abdominal discomfort) are common, especially at initiation. These can be minimized by starting with a low dose, titrating slowly, and taking with meals.
- Patients should be educated about the symptoms of lactic acidosis and advised to seek immediate medical attention if they occur.
- Metformin should be temporarily discontinued before or at the time of iodinated contrast imaging procedures and for surgery requiring restricted food/fluid intake, and restarted only after renal function is stable.
- Regular monitoring of renal function is crucial, as metformin is primarily renally eliminated, and accumulation can lead to lactic acidosis.
Alternative Therapies
- Sulfonylureas (e.g., glipizide, glyburide)
- DPP-4 inhibitors (e.g., sitagliptin, saxagliptin)
- SGLT2 inhibitors (e.g., empagliflozin, canagliflozin)
- GLP-1 receptor agonists (e.g., liraglutide, semaglutide)
- Thiazolidinediones (e.g., pioglitazone)
- Insulin therapy
Cost & Coverage
Average Cost:
Low to moderate per 30 tablets
Generic Available:
Yes
Insurance Coverage:
Tier 1 (Generic)
General Drug Facts
If your symptoms or health issues persist or worsen, it is essential to contact your doctor for further guidance. To ensure your safety, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so it's a good idea to check with your pharmacist. If you have any questions or concerns about this medication, don't hesitate to discuss them with your doctor, nurse, pharmacist, or other healthcare provider. In the event of a suspected overdose, immediately call your local poison control center or seek medical attention. When seeking help, be prepared to provide information about the medication taken, the amount, and the time it happened.