Buy Metformin (Glucophage) — Online Prescription
Metformin (brand name Glucophage) is the first-line medicine for type 2 diabetes and one of the cheapest prescriptions in America. This guide covers how it works, its side effects (and how to stop the diarrhea), what the big trials show about weight loss, PCOS use, a dosage chart, and what you'll pay.
Medically reviewed Medically reviewed by Darcey Melnyk, Pharmacist — NPI 1740713718 · Last updated 2026-09-25
| Active ingredient | Metformin hydrochloride |
|---|---|
| Dosage form | Tablet (500, 850, 1000 mg), extended-release tablet (500, 750, 1000 mg), oral solution |
| Administration route | Oral |
Indications: 1 INDICATIONS & USAGE Metformin hydrochloride tablets are indicated as an adjunct to diet and exercise to improve glycemic control in adults and pediatric patients 10 years of age and older with type 2 diabetes mellitus. Metformin hydrochloride tablets are biguanide indicated as an adjunct to diet and exercise to improve glycemic control in adults and pediatric patients 10 years of age and older with type 2 diabetes mellitus. ( 1 )
Boxed warning: BOXED WARNING WARNING: LACTIC ACIDOSIS 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 pain. Metformin associated lactic acidosis was characterized by elevated blood lactate levels (>5 mmol/Liter), anion gap acidosis (without evidence of ketonuria or ketonemia), an increased lactate/pyruvate ratio; and metformin plasma …
Contraindications: 4 CONTRAINDICATIONS Metformin hydrochloride tablets are contraindicated in patients with: Severe renal impairment (eGFR below 30 mL/min/1.73 m 2 ) [ see Warnings and Precautions (5.1) ]. Hypersensitivity to metformin. Acute or chronic metabolic acidosis, including diabetic ketoacidosis, with or without coma. Severe renal impairment (eGFR below 30 mL/min/1.73 m 2 ) ( 4 , 5.1 ) Hypersensitivity to metformin ( 4 ) Acute or chronic metabolic acidosis, including diabetic ketoacidosis, with or without…
openFDA label data — Updated 2026-09-29Metformin (brand name Glucophage, now sold only as generic) is the first-line prescription pill for type 2 diabetes. It lowers blood sugar mainly by cutting how much sugar your liver releases. It's also used off-label for prediabetes and PCOS. It is not insulin and not a GLP-1 like Ozempic, and on its own it rarely causes low blood sugar. The main side effect is diarrhea (53% with regular tablets in the FDA trial, 10% with extended-release), which a slow start usually controls. Weight loss is real but small: about 2% of body weight on average. Generic metformin costs a few dollars a month.
What metformin is used for
Metformin hydrochloride belongs to the biguanide class and has been a first-line type 2 diabetes treatment for decades. It's cheap, it doesn't cause weight gain, and on its own it rarely causes hypoglycemia. The original brand, Glucophage, is discontinued in the US, so you'll get generic metformin, either immediate-release (IR) or extended-release (ER/XR). Metformin is also an ingredient in combination pills such as Janumet (with sitagliptin), Synjardy (with empagliflozin) and Xigduo XR (with dapagliflozin).
How metformin works
Metformin works in three places, and none of them involves forcing your pancreas to release insulin. That's why it rarely causes low blood sugar on its own.
Metformin side effects
Most metformin side effects are in the gut, and most are worst in the first few weeks. These are the rates from the FDA trial of regular (immediate-release) metformin:
Source: metformin hydrochloride FDA prescribing information, Table 1. Less common (1–5%): abnormal stools, low blood sugar, muscle aches, lightheadedness, taste changes such as a metallic taste, and increased sweating.
Side effects in women vs. men. The label doesn't list any sex-specific side effects. The rates above apply to everyone. There are two practical differences:
Ovulation can return
- Unplanned pregnancy
- The FDA label warns that metformin may restart ovulation in some women who weren't ovulating, which is common with PCOS. Use contraception if you're not planning a pregnancy.
- B12 and anemia
- Heavy periods plus long-term metformin can compound iron or B12 shortfalls. Ask about periodic blood counts.
No proven sexual side effects
- Erectile dysfunction
- ED is not a listed side effect. Diabetes itself is a major cause of ED, so better glucose control tends to help, not hurt.
- Same GI profile
- Diarrhea, nausea and gas at the same rates. The same slow-start strategy applies.
Metformin diarrhea: why it happens and how to stop it
Metformin reaches much higher concentrations in the intestine than in the blood. It's thought to change how the gut handles glucose and bile acids and to shift gut bacteria, which speeds up bowel movements. The single biggest fix is the tablet type:
Source: FDA prescribing information for metformin tablets (n=141) and extended-release tablets (n=781). Placebo rates were 12% and 3% for diarrhea, respectively.
- Start low, go slowMany prescribers start at 500 mg once a day and add 500 mg a week. If a step upsets your stomach, ask about staying at the previous dose a bit longer before moving up.
- Always take it with a mealTake it with food, never on an empty stomach. Your largest meal of the day is the easiest on the gut.
- Go easy on heavy mealsVery large, greasy or sugary meals make the first weeks harder. Smaller, balanced meals help.
- Ask about extended-releaseYou take the same total daily dose once a day with dinner, with a fraction of the diarrhea. Swallow it whole and never cut or crush it.
- Give it 2–4 weeksGI effects usually fade as your body adjusts. Call your prescriber sooner if diarrhea is severe, or if you feel dizzy or dehydrated.
Metformin for weight loss: what the trials show
"Metformin weight loss" gets more searches than almost any other question about this drug, and a lot of what's online oversells it. The best evidence is the Diabetes Prevention Program (DPP), a trial of 3,234 adults with prediabetes who took 850 mg of metformin twice daily, a lifestyle program, or placebo:
Source: Apolzan et al., Annals of Internal Medicine 2019 (DPP Outcomes Study). Average weight change over the DPP was −0.1 kg on placebo, −2.1 kg on metformin and −5.6 kg with the lifestyle program (NEJM 2002).
Here's what that means in practice:
- The average loss is small: about 2% of body weight. For a 200 lb person that's roughly 4 lb. It lasted, though: metformin users kept about 2% off through 10 years of follow-up, in step with how consistently they took it.
- About 1 in 4 people respond well. Those who lost 5% or more in the first year kept off an average of about 6% of their weight for years afterward. In the DPP, first-year weight loss was the best predictor of long-term results.
- "2 month metformin weight loss results" are usually modest. Early losses are partly from reduced appetite during the GI adjustment period.
- Is 500 mg a low dose for weight loss? Yes. It's a starting dose. The DPP used 1,700 mg a day, and no metformin dose is FDA-approved for weight loss.
- Metformin without diabetes. Prescribers do use it off-label for prediabetes, PCOS and insulin resistance, where weight is a secondary benefit. For weight loss as the main goal, FDA-approved obesity medicines are far more effective. See the comparison below.
Sources: DPP Research Group, Diabetes Care 2012 (2.06% vs. 0.02%); Wilding et al., NEJM 2021 (STEP 1). Semaglutide 2.4 mg is the Wegovy dose. See our Ozempic (semaglutide) page.
Metformin for PCOS
In polycystic ovary syndrome, insulin resistance drives higher insulin levels. Higher insulin pushes the ovaries to make more androgens, which disrupts ovulation. Metformin lowers insulin levels, and that can help in a few ways:
- Metabolic health. The 2023 International PCOS Guideline supports metformin together with lifestyle changes in adults with PCOS, especially with a BMI of 25 or higher, mainly for weight, insulin resistance and metabolic outcomes.
- Cycles and ovulation. Metformin can make periods more regular in some women. For fertility treatment, though, letrozole is the first-line ovulation drug, and metformin is at most an add-on.
- Pregnancy can happen sooner than expected. The FDA label specifically warns about restored ovulation. Plan contraception accordingly.
- It isn't a PCOS cure. Acne and excess hair usually need other treatments, such as hormonal contraception or spironolactone.
Metformin dosage chart and best time to take it
| Form | Tablet strengths | Usual start | How to increase | Maximum |
|---|---|---|---|---|
| Immediate-release (adults) | 500, 850, 1000 mg | 500 mg twice daily or 850 mg once daily, with meals | +500 mg weekly or +850 mg every 2 weeks | 2,550 mg/day, divided. Above 2,000 mg is often better tolerated 3 times a day. |
| Extended-release (adults) | 500, 750, 1000 mg | 500 mg once daily with the evening meal | +500 mg weekly | 2,000 mg once daily |
| Immediate-release (children 10–16) | 500 mg | 500 mg twice daily with meals | +500 mg weekly | 2,000 mg/day, divided |
Many prescribers start even more gently than the label to spare the stomach. A typical example schedule for immediate-release (yours may differ):
500 mg once daily with dinner
500 mg twice daily, with breakfast and dinner (1,000 mg/day)
500 mg with breakfast and 1,000 mg with dinner (1,500 mg/day)
1,000 mg twice daily (2,000 mg/day), a common target dose. A classic dose-response trial found most of the glucose-lowering benefit by 1,500–2,000 mg a day.
Immediate-release: with breakfast and dinner, or with each meal at higher doses. Extended-release: once a day with the evening meal, swallowed whole. Evening dosing targets the liver's overnight sugar release, which is what drives high morning readings. With some ER brands you may see what looks like a whole tablet in your stool. That's the empty tablet shell after the medicine has been released.
How long metformin takes to work
Glucose starts to fall. You won't feel it. Your meter will show it. Stomach side effects peak around now.
Fasting readings trend down at each dose step. GI symptoms usually start to settle.
A1C recheck. A1C reflects about 3 months of glucose. In the FDA trial, A1C dropped 1.4 points, while it rose 0.4 on placebo.
Weight trend is clear. This is when you'll know whether you're one of the roughly 1 in 4 people with meaningful weight loss.
Kidneys, lactic acidosis and vitamin B12
Rarely, metformin can cause lactic acidosis, a dangerous buildup of acid in the blood that has caused deaths. It starts subtly, with unusual muscle pain, trouble breathing, unusual sleepiness, stomach pain and feeling cold or weak. The risk is highest with poor kidney function, age 65+, contrast-dye imaging, surgery, low-oxygen states such as acute heart failure, heavy drinking, liver disease, and drugs like topiramate. If you suspect it, stop metformin and get emergency care.
Common early effects
- Loose stools, gas or nausea in the first weeks
- A metallic taste
- Mild appetite loss
Needs a check
- Diarrhea lasting more than a few weeks
- Numbness or tingling in your feet, or fatigue (check B12)
- A CT scan with contrast or surgery coming up
- Vomiting illness, or you can't eat or drink (you may need to pause doses)
Possible lactic acidosis
- Unusual muscle pain with weakness
- Fast or difficult breathing
- Unusual sleepiness or confusion
- Severe stomach pain with feeling cold or dizzy
| Kidney function (eGFR, mL/min/1.73 m²) | What the FDA label says |
|---|---|
| 45 or higher | Metformin can be used. Check kidney function at least yearly. |
| 30–45 | Don't start metformin. If you're already taking it, your prescriber reassesses benefit vs. risk. |
| Below 30 | Contraindicated. Stop metformin. |
Vitamin B12. In 29-week trials, about 7% of patients with normal B12 dropped below normal on metformin. It's reversible with supplements. The label recommends blood counts yearly and a B12 level every 2–3 years. Numbness or tingling in the feet can come from B12 deficiency or diabetic nerve damage, so don't assume which one it is.
Contrast dye. For CT scans with iodinated contrast, metformin is paused if your eGFR is 30–60, you have liver disease, alcoholism or heart failure, or the contrast goes into an artery. It's restarted 48 hours later once kidney function is confirmed stable. Always tell the imaging center you take metformin.
Alcohol, foods to avoid and interactions
No food is strictly off-limits with metformin. These are the habits that actually matter:
- Take every dose with a meal
- Fiber-rich, balanced meals: vegetables, legumes, whole grains, lean protein
- Spreading carbohydrates evenly across the day
- If you drink, a moderate amount, with food
- Binge drinking or heavy regular alcohol use (lactic acidosis risk)
- Sugary drinks and large refined-carb meals, which raise glucose faster than metformin can offset
- Very large, greasy meals in the first weeks (more GI upset)
- Skipping meals while also taking insulin or a sulfonylurea (low blood sugar risk)
| Interacting drug or substance | What can happen |
|---|---|
| Alcohol (excessive) | Raises lactic acidosis risk |
| Iodinated contrast dye | Can temporarily reduce kidney function. Metformin may be paused around the scan. |
| Topiramate, zonisamide, acetazolamide (carbonic anhydrase inhibitors) | Can cause acidosis on their own and add to the risk with metformin |
| Cimetidine, dolutegravir, ranolazine, vandetanib | Raise metformin blood levels |
| Insulin and sulfonylureas (glipizide, glyburide, glimepiride) | Higher risk of low blood sugar in combination. The other drug's dose may need lowering. |
| Steroids, thiazide diuretics, some antipsychotics, thyroid hormone | Raise blood sugar and can blunt metformin's effect |
Metformin vs. Ozempic, Jardiance and berberine
| Metformin | Ozempic (semaglutide) | Jardiance (empagliflozin) | Berberine | |
|---|---|---|---|---|
| What it is | Biguanide pill | GLP-1 agonist | SGLT2 inhibitor pill | Plant-derived supplement |
| How it's taken | 1–3 times daily with meals | Weekly injection | Once daily | Usually 2–3 times daily |
| Weight effect | Neutral to small loss (~2%) | Substantial loss | Modest loss | Small, inconsistent data |
| Extra proven benefits | Decades of safety data, very low cost | Cardiovascular benefit in high-risk patients | Heart failure and kidney protection | None established by large outcome trials |
| Typical monthly cost (cash) | About $4–15 | About $950–1,050 list | Brand price. Ask for a quote. | Varies. Sold as a supplement, not regulated as a drug. |
| Prescription | Yes | Yes | Yes | No. Not FDA-reviewed for effectiveness. |
These aren't really either/or choices. Current diabetes guidelines often add a GLP-1 or SGLT2 drug to metformin for people with heart disease, kidney disease or obesity rather than replacing it. Berberine vs. metformin: berberine has small studies showing glucose-lowering effects, but it's a supplement with no standardized dose or quality control. It can also interact with other drugs, and it isn't a substitute for a prescribed diabetes medicine. If you want to take it with metformin, talk to your pharmacist first, since the two can add up.
Buy metformin: prescription, price and savings
- Prescription required, no OTC version. Metformin is prescription-only in the US. A website selling it "without a prescription" isn't a legitimate pharmacy. It's also not a controlled substance, so any primary care provider or licensed telehealth prescriber can send it to us.
- Online prescription, local pickup or delivery. Have your prescriber e-prescribe to Arrow Pharmacy, or transfer an existing prescription. We can usually fill it the same day. Ask about next-day delivery in the Hartford area.
- Generic is cheap, and a 90-day fill is cheaper still. Pharmacies pay about 1.5 cents per 500 mg tablet at wholesale (NADAC, below). Without insurance, generic metformin is often cheaper than a typical copay. See the price table below, or call for a current cash price.
- Ask about ER if the stomach effects are a problem. Extended-release metformin is also inexpensive as a generic. Switching is a quick call to your prescriber.
- NDMA recalls. Between 2020 and 2022, some ER metformin lots were recalled for NDMA impurities. FDA testing did not find the problem in immediate-release metformin. If you're worried, ask us to check your specific manufacturer and lot against FDA recall notices rather than stopping your medicine.
Call (860) 522-9289 to fill or transfer a prescription, or to ask a pharmacist about side effects or switching to ER. We can also bundle metformin with your other daily medicines in Medicine-on-Time packaging.
No active shortage reported — No shortage records found for this generic name.
FDA openFDA — Updated 2026-09-29National Average Drug Acquisition Cost (NADAC): $0.015 per tablet (METFORMIN HCL 500 MG TABLET). This is the average price pharmacies pay wholesalers — not your out-of-pocket cost — published by CMS for pricing transparency.
CMS NADAC — Updated 2026-09-29Metformin (Glucophage) Prices in the USA
| Dosage | Brand-name avg. price | Generic avg. price |
|---|---|---|
| Metformin 500 mg, 60 tablets (30 days of the usual starting dose) | Glucophage brand discontinued in the US | $4–15 |
| Metformin 1000 mg, 180 tablets (90 days at 2,000 mg/day) | Glucophage brand discontinued in the US | $10–30 |
| Metformin ER (extended-release) 500 mg, 120 tablets (30 days at 2,000 mg/day) | Glucophage XR brand discontinued in the US | $8–30 |
Frequently asked questions
What is metformin used for?
Metformin is FDA-approved to lower blood sugar in type 2 diabetes, in adults and children 10 and older, alongside diet and exercise. It is also widely prescribed off-label for prediabetes (it cut progression to diabetes by 31% in the Diabetes Prevention Program), for insulin resistance in polycystic ovary syndrome (PCOS), and sometimes to limit weight gain caused by certain psychiatric medications. It is not used for type 1 diabetes.
Is Glucophage the same as metformin?
Yes. Glucophage was the original brand name for metformin. The brand (and Glucophage XR) is no longer sold in the US, and the FDA confirmed in 2019 that this was a business decision, not a safety issue. Every metformin prescription filled today is generic, whether immediate-release or extended-release.
Is metformin insulin, or a GLP-1 like Ozempic?
Neither. Metformin is a biguanide pill. It doesn't contain insulin or make your pancreas release more of it — it mainly reduces the sugar your liver releases and helps your body use its own insulin better. It isn't a GLP-1 drug either, although research shows it modestly raises your natural GLP-1 levels in the gut. GLP-1 medicines such as semaglutide (Ozempic) are separate, much more expensive drugs that act far more strongly on appetite.
Is 500 mg of metformin a low dose?
Yes. 500 mg is the lowest standard tablet and the usual starting dose. Most adults with type 2 diabetes end up on 1,500–2,000 mg a day, which is where a classic dose-response trial found most of the blood-sugar benefit; the FDA maximum is 2,550 mg a day for immediate-release and 2,000 mg for extended-release. For weight loss specifically, there is no FDA-approved metformin dose — the Diabetes Prevention Program used 850 mg twice a day.
How long does metformin take to work?
Metformin starts lowering blood sugar within the first days, and home fasting readings usually trend down over the first 1–2 weeks at each dose step. Because doses are increased gradually over several weeks, the full effect takes longer, and your A1C (a roughly 3-month average) is normally rechecked about 3 months after starting or changing the dose. In the FDA trial, A1C fell 1.4 points on metformin while it rose 0.4 on placebo over 29 weeks.
What are the signs that metformin is working?
You usually can't feel metformin working. The real signs are numbers: lower fasting glucose readings on your meter, and a lower A1C at your next lab check. If you had high-blood-sugar symptoms such as frequent urination, thirst or fatigue, those may ease as your numbers improve. Stomach side effects are not a sign that it's working, and they typically fade within a few weeks.
Why does metformin cause diarrhea, and how do I stop it?
Metformin reaches high concentrations in the intestine, where it's thought to change how the gut handles glucose, bile acids and gut bacteria, which can speed up bowel movements. In the FDA trial, diarrhea affected 53% of people on immediate-release metformin versus 12% on placebo, but only 10% on extended-release (versus 3% on placebo). To reduce it: start low and increase slowly, always take it with a meal, avoid very large or high-fat meals early on, and ask your prescriber about switching to extended-release. Call your prescriber if diarrhea is severe, lasts more than a few weeks, or comes with dizziness or signs of dehydration.
When is the best time to take metformin?
With meals. Immediate-release metformin is usually taken with breakfast and dinner (or with each meal at higher doses). Extended-release metformin is taken once a day with the evening meal and must be swallowed whole — never crushed, cut or chewed. Taking a single 500 mg dose with your largest meal of the day is a common gentle way to start.
Can I take metformin without food?
It's not recommended. The label says to take metformin with meals, and taking it on an empty stomach makes nausea, stomach pain and diarrhea much more likely. Metformin alone rarely causes low blood sugar, so the reason for food is stomach tolerance, not hypoglycemia (unless you also take insulin or a sulfonylurea).
Can you drink alcohol while taking metformin?
Moderate drinking with food is generally considered acceptable for most people, but the FDA label warns against excessive alcohol because it raises the risk of lactic acidosis, the rare but serious complication behind metformin's boxed warning. Binge drinking is the real danger. Don't skip or adjust doses on your own around drinking — ask your prescriber what's safe for you.
Is metformin bad for your kidneys?
No — metformin does not damage the kidneys. It is removed from the body by the kidneys, so if your kidneys are already weak it can build up. That's why the label requires a kidney function test (eGFR) before starting and periodically after: metformin should not be used below an eGFR of 30, isn't started between 30 and 45, and needs a risk-benefit review if your eGFR falls below 45 while you're on it.
Does metformin cause hair loss?
Hair loss is not listed as a side effect in metformin's FDA label. Hair thinning in people taking metformin usually has another cause — PCOS itself, thyroid disease, poorly controlled diabetes, or rapid weight loss. Long-term metformin can lower vitamin B12, and severe B12 deficiency can affect hair and nails, which is one more reason for periodic B12 checks.
Does metformin make you tired or cause headaches?
It can for some people. In the FDA trial, weakness or fatigue (asthenia) was reported by 9% on metformin versus 6% on placebo, and headache by 6% versus 5%. Persistent tiredness after years on metformin is worth a vitamin B12 check, since the label reports previously normal B12 levels dropping below normal in about 7% of patients in 29-week trials.
How long does metformin stay in your system?
Metformin's plasma half-life is about 6.2 hours, and about 90% of it leaves the body through the kidneys within 24 hours. In the blood as a whole (including red blood cells) the half-life is longer, about 17.6 hours. That's why it's dosed once to three times daily, and why it builds up if your kidneys aren't clearing it well.
Can I take metformin while pregnant?
Metformin is sometimes used in pregnancy, but the decision is individual. The FDA label notes published studies haven't shown a clear link to major birth defects or miscarriage, and uncontrolled diabetes itself raises the risk of birth defects substantially (the label cites 6–10% at an A1C above 7, and up to 20–25% above 10). Insulin remains the standard treatment for many pregnant patients. Plan any pregnancy with your prescriber and OB rather than starting or stopping metformin on your own.
Can I buy metformin over the counter?
No. Metformin is prescription-only in the US and there is no OTC version. You can get a prescription from your primary care provider or a licensed telehealth service, and we can fill it the same day. It isn't a controlled substance, and generic metformin is inexpensive — usually cheaper than a copay even without insurance.
What should I do if I miss a dose of metformin?
Take it with your next meal if you remember within a few hours. If it's almost time for your next dose, skip the missed one. Never double up — a double dose mostly adds stomach side effects without extra benefit.
Sources
- Metformin Hydrochloride Tablets and Extended-Release Tablets — FDA-approved prescribing information — U.S. National Library of Medicine (DailyMed) / U.S. FDA
- Reduction in the Incidence of Type 2 Diabetes with Lifestyle Intervention or Metformin (Diabetes Prevention Program) — New England Journal of Medicine (2002)
- Long-Term Safety, Tolerability, and Weight Loss Associated With Metformin in the Diabetes Prevention Program Outcomes Study — Diabetes Care (2012), via PubMed
- Long-Term Weight Loss With Metformin or Lifestyle Intervention in the Diabetes Prevention Program Outcomes Study — Annals of Internal Medicine (2019)
- Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1) — New England Journal of Medicine (2021)
- Efficacy of metformin in type II diabetes: results of a double-blind, placebo-controlled, dose-response trial — American Journal of Medicine (1997), via PubMed
- International Evidence-based Guideline for the Assessment and Management of Polycystic Ovary Syndrome (2023) — Monash University / NHMRC Centre for Research Excellence in PCOS
- Determination That GLUCOPHAGE and GLUCOPHAGE XR Were Not Withdrawn From Sale for Reasons of Safety or Effectiveness — Federal Register / U.S. FDA
- FDA Updates and Press Announcements on NDMA in Metformin — U.S. Food and Drug Administration
- NADAC (National Average Drug Acquisition Cost) — METFORMIN HCL 500 MG TABLET — CMS
- openFDA Drug Shortages — U.S. FDA
- Controlled Substances List — U.S. DEA Diversion Control Division