Metformin; Uses, Dosage, Side Effects, Drug Interactions

Last updated: February 7, 2026Reviewed date: February 7, 2026Reading time: 6 min read

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Article Summary

Metformin is a biguanide hypoglycemic agent used in the treatment of non-insulin-dependent diabetes mellitus not responding to dietary modification. Metformin improves glycemic control by improving insulin sensitivity and decreasing intestinal absorption of glucose. (From Martindale, The Extra Pharmacopoeia, 30th ed, p289) Metformin is an agent belonging to the biguanide class of antidiabetics with antihyperglycemic activity. Metformin is associated with a very low incidence of lactic acidosis. This agent helps reduce...

Key Takeaways

This article explains Mechanism of Action of Metformin in simple medical language.
This article explains Indications of Metformin in simple medical language.
This article explains Dosage of Metformin in simple medical language.
This article explains Side Effects of Metformin in simple medical language.

Educational health guideWritten for patient understanding and clinical awareness.

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Emergency safety firstUrgent warning signs are highlighted below.

Seek urgent medical care if you notice

These warning signs are general safety guidance. Local emergency numbers and clinical judgment should always come first.

Severe symptoms, breathing difficulty, fainting, confusion, or rapidly worsening illness.
New weakness, severe pain, high fever, or symptoms after a serious injury.
Any symptom that feels urgent, unusual, or unsafe for the patient.

Emergency now

Use emergency care for severe, sudden, rapidly worsening, or life-threatening symptoms.

See a doctor

Book a professional medical evaluation if symptoms persist, worsen, recur often, affect daily activities, or occur in a high-risk patient.

Learn safely

Use this article to understand possible causes, tests, treatment options, prevention, and questions to ask your clinician.

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Metformin is a biguanide hypoglycemic agent used in the treatment of non-insulin-dependent diabetes mellitus not responding to dietary modification. Metformin improves glycemic control by improving insulin sensitivity and decreasing intestinal absorption of glucose. (From Martindale, The Extra Pharmacopoeia, 30th ed, p289)

Metformin is an agent belonging to the biguanide class of antidiabetics with antihyperglycemic activity. Metformin is associated with a very low incidence of lactic acidosis. This agent helps reduce LDL cholesterol and triglyceride levels, and is not associated with weight gain, and prevents the cardiovascular complications of insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।" data-rx-term="diabetes" data-rx-definition="Diabetes is a condition where blood sugar stays too high because insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।">diabetes. Metformin is not metabolized and is excreted unchanged by the kidneys.

Definition

Metformin is a biguanide antihyperglycemic agent used for treating non-insulin-dependent diabetes mellitus (NIDDM). It is the first-line medication for the treatment of type 2 diabetes, particularly in people who are overweight. It is also used in the treatment of polycystic ovary syndrome. Limited evidence suggests metformin may prevent the cardiovascular disease and cancer complications of insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।" data-rx-term="diabetes" data-rx-definition="Diabetes is a condition where blood sugar stays too high because insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।">diabetes. It improves glycemic control by decreasing hepatic glucose production, decreasing glucose absorption and increasing insulin-mediated glucose uptake. Metformin may induce weight loss and is the drug of choice for obese NIDDM patients. Use of metformin is associated with modest weight loss.

Mechanism of Action of Metformin

Metformin’s mechanisms of action differ from other classes of oral antihyperglycemic agents. Metformin decreases blood glucose levels by decreasing hepatic glucose production, decreasing intestinal absorption of glucose, and improving insulin sensitivity by increasing peripheral glucose uptake and utilization. These effects are mediated by the initial activation by metformin of AMP-activated protein kinase (AMPK), a liver enzyme that plays an important role in insulin signaling, whole body energy balance, and the metabolism of glucose and fats. Activation of AMPK is required for metformin’s inhibitory effect on the production of glucose by liver cells. Increased peripheral utilization of glucose may be due to improved insulin binding to insulin receptors. Metformin administration also increases AMPK activity in skeletal muscle. AMPK is known to cause GLUT4 deployment to the plasma membrane, resulting in insulin-independent glucose uptake. The rare side effect, lactic acidosis, is thought to be caused by the decreased liver uptake of serum lactate, one of the substrates of gluconeogenesis. In those with healthy renal function, the slight excess is simply cleared. However, those with a severe renal impairment may accumulate clinically significant serum lactic acid levels. Other conditions that may precipitate lactic acidosis include severe hepatic disease and acute/decompensated heart failure.

Indications of Metformin

insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।" data-rx-term="diabetes" data-rx-definition="Diabetes is a condition where blood sugar stays too high because insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।">Diabetes, Type 2
Polycystic Ovary Syndrome
insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।" data-rx-term="diabetes" data-rx-definition="Diabetes is a condition where blood sugar stays too high because insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।">Diabetes, Type 3c
Insulin Resistance Syndrome
Female Infertility
For use as an adjunct to diet and exercise in adult patients (18 years and older) with NIDDM. May also be used for the management of metabolic and reproductive abnormalities associated with polycystic ovary syndrome (PCOS). Jentadueto is for the treatment of patients when both linagliptin and metformin is appropriate.

Dosage of Metformin

Strengths: 500 mg; 750 mg; 850 mg; 1000 mg; 500 mg/5 mL

insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।" data-rx-term="diabetes" data-rx-definition="Diabetes is a condition where blood sugar stays too high because insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।">Diabetes Type 2

Immediate-release

Initial dose: 500 mg orally twice a day or 850 mg orally once a day
Dose titration: Increase in 500 mg weekly increments or 850 mg every 2 weeks as tolerated
Maintenance dose: 2000 mg daily in divided doses
Maximum dose: 2550 mg/day

Extended-release

Initial dose: 500 to 1000 mg orally once a day
Dose titration: Increase in 500 mg weekly increments as tolerated
Maintenance dose: 2000 mg daily
Maximum dose: 2500 mg daily

Pediatric insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।" data-rx-term="diabetes" data-rx-definition="Diabetes is a condition where blood sugar stays too high because insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।">Diabetes Type 2

10 years or older
Immediate-release

Initial dose: 500 mg orally twice a day
Dose titration: Increase in 500 mg weekly increments as tolerated
Maintenance dose: 2000 mg daily
Maximum dose: 2000 mg daily

Side Effects of Metformin

Most common

physical weakness (asthenia)
diarrhea
gas (flatulence)
symptoms of weakness, muscle pain (myalgia)
upper respiratory tract infection
low blood sugar (hypoglycemia)
abdominal pain (GI complaints), lactic acidosis (rare)
low blood levels of vitamin B-12
nausea,vomiting
chest discomfort
chills, dizziness
bloating/abdominal distention
constipation
heartburn

More common

Less common

Abnormal stools
bad, unusual, or unpleasant (after) taste
change in taste
difficulty with moving
discoloration of the fingernails or toenails
flu-like symptoms
joint pain
rash
runny nose
sneezing
stuffy nose
swollen joints

Drug Interactions of Metformin

Metformin may interact with following drugs, supplements & may decrease the efficacy of the drug

angiotensin converting enzyme inhibitors (ACEIs; captopril, enalapril, ramipril)
alcohol
antipsychotic medications (e.g., chlorpromazine, haloperidol, olanzapine,
birth control pills
bupropion
corticosteroids (e.g., dexamethasone, prednisone)
diabetic drugs (e.g., glyburide, insulin, repaglinide, sitagliptin)
diuretics (e.g., furosemide, hydrochlorothiazide)
HIV protease inhibitors (e.g., atazanavir, indinavir, ritonavir, saquinavir)
phenytoin
quinolone antibiotics (e.g., levofloxacin, moxifloxacin)
selective serotonin reuptake inhibitors (SSRIs; citalopram, fluoxetine, sertraline paroxetine,
trimethoprim
vancomycin
verapamil
warfarin

Pregnancy & Lactation of Metformin

FDA Pregnancy Category B

Pregnancy

This medication should not be used during pregnancy. If you become pregnant while taking this medication, contact your doctor immediately.

Lactation

Metformin is believed to pass into breast milk. This medication should not be used if you are breastfeeding.

References

Metformin; Uses, Dosage, Side Effects, Drug Interactions

Safety note: This is not a prescription or diagnosis. For severe symptoms, pregnancy danger signs, children with serious illness, chest pain, breathing difficulty, stroke-like weakness, or major injury, seek urgent care.

Which doctor may help?

Start with a registered doctor or the nearest qualified health center.

What to tell the doctor

Write when the problem started and how it changed.
Bring old prescriptions, investigation reports, and current medicines.
Write allergies, pregnancy status, diabetes, kidney/liver disease, and major past illnesses.
Bring one family member if the patient is weak, elderly, confused, or a child.

Questions to ask

What is the most likely cause of my symptoms?
Which danger signs mean I should go to hospital quickly?
Which tests are necessary now, and which can wait?
How should I take medicines safely and what side effects should I watch for?
When should I come for follow-up?

Tests to discuss

Vital signs: temperature, pulse, blood pressure, oxygen saturation
Basic physical examination by a clinician
CBC, urine test, blood sugar, or imaging only when clinically needed

Avoid these mistakes

Do not use antibiotics, steroid tablets/injections, or strong painkillers without proper medical advice.
Do not hide pregnancy, kidney disease, ulcer, allergy, or blood thinner use.
Do not delay emergency care when danger signs are present.

Medicine safety and first-aid guide

This section is for patient education only. It does not replace a doctor, pharmacist, or emergency care.

Safe first steps

Avoid heavy lifting, sudden bending, and prolonged bed rest.
Use comfortable posture and gentle movement as tolerated.
Discuss physiotherapy, X-ray, or MRI only when clinically needed.

OTC medicine safety

For mild back pain, pain-relief medicine may be discussed with a doctor or pharmacist.
Avoid repeated painkiller use if you have kidney disease, stomach ulcer, uncontrolled blood pressure, or are taking blood thinners.

Avoid these mistakes

Do not start antibiotics without a proper medical decision.
Do not use steroid tablets or injections casually for quick relief.
Do not delay emergency care because of home remedies.

Get urgent help if

Back pain with leg weakness, numbness around private area, loss of urine/stool control, fever, cancer history, or major injury needs urgent care.

Medicine names, dose, and timing must be decided by a qualified clinician or pharmacist after checking age, pregnancy, allergy, other diseases, and current medicines.

For rural patients and family caregivers

Patient health record and symptom diary

Write your symptoms, medicines already taken, test results, and questions before visiting a doctor. This note stays on your device unless you print or copy it.

Doctor to discuss: Medicine doctor / pediatrician for children / qualified clinician

Tests to discuss with doctor

Temperature chart and hydration assessment
CBC with platelet count if fever persists or dengue/other infection is possible
Urine test, malaria/dengue tests, chest evaluation, or blood culture only when clinically indicated

Questions to ask

What is the most likely cause of my symptoms?
Which warning signs mean I should go to emergency care?
Which tests are really needed now?
Which medicines are safe for my age, pregnancy status, allergy, kidney/liver/stomach condition, and current medicines?
Do I need antibiotics, or is this more likely viral?

Emergency warning signs such as chest pain, severe breathing difficulty, sudden weakness, confusion, severe dehydration, major injury, or loss of bladder/bowel control need urgent medical care. Do not wait for online information.

Go to emergency care if you notice:

Severe or rapidly worsening symptoms
Breathing difficulty, chest pain, fainting, confusion, severe weakness, major injury, or severe dehydration

Doctor / service to discuss: Qualified healthcare provider; specialist depends on symptoms and examination.

Step 1
Check danger signs first

If danger signs are present, seek emergency care and do not wait for online information.
Step 2
Record the symptom story

Write when symptoms started, severity, medicines already taken, allergies, pregnancy status, and test results.
Step 3
Visit a qualified clinician

A doctor, nurse, or qualified healthcare provider can examine you and decide which tests or treatment are needed.
Step 4
Do only useful tests

Do tests after clinical assessment. Avoid unnecessary tests, random antibiotics, or repeated medicines without diagnosis.
Step 5
Follow up and return early if worse

If symptoms worsen, new warning signs appear, or treatment is not helping, return for review quickly.

Rural patient practical tips

Take a written symptom diary and all previous prescriptions/test reports.
Do not hide medicines already taken, even herbal or over-the-counter medicines.
Ask which warning signs mean urgent referral to hospital.

This roadmap is for education. A real diagnosis and treatment plan requires history, examination, and clinical judgment.

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Emergency first: Severe chest pain, breathing trouble, unconsciousness, stroke signs, severe injury, heavy bleeding, or rapidly worsening symptoms need urgent local medical care now.

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Frequently Asked Questions

Is this article a replacement for a doctor?

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When should I seek urgent care?

Seek urgent care for severe symptoms, rapidly worsening condition, breathing difficulty, severe pain, neurological changes, or any emergency warning sign.

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