Metformin Dosage Guide: 500mg, 850mg & 1000mg, Max Daily Dose & Best Time to Take
Metformin dosage at a glance
Most adults start metformin at 500mg once or twice daily with meals. The dose is then raised slowly to a usual maintenance dose of 1,500–2,000mg a day.
Metformin is a first-line medicine for type 2 diabetes. It lowers blood sugar by reducing the glucose your liver releases and helping your body respond better to insulin. The right dose depends on your blood sugar, kidney function, the tablet type and how well you tolerate it.
Quick answer
- Starting dose: 500mg once or twice daily, or 850mg once daily, with meals
- Usual maintenance dose: 1,500–2,000mg per day, split across meals
- Maximum dose (regular tablets): 3,000mg per day in 3 divided doses
- Maximum dose (extended-release, XR): 2,000mg once daily with the evening meal
- Best time to take: with or straight after a meal, never on an empty stomach
- Kidney limit: dose is reduced when eGFR is 30–44 and metformin is stopped below 30
Metformin is a prescription medicine in Malaysia. Your doctor sets your dose. This guide explains how dosing works so you know what to expect.
Metformin strengths: 500mg, 850mg and 1000mg
Metformin comes in three main strengths, as regular (immediate-release) or extended-release (XR) tablets. XR releases the drug slowly, so it is taken once a day and usually causes fewer stomach side effects.
| Strength | Type | Typical use | How often | Max per day | Shop at DOC |
|---|---|---|---|---|---|
| Metformin HCl 500mg | Regular | Starting dose; fine dose steps | 1–3 times daily with meals | 3,000mg (6 tablets) | [Metformin 500mg] |
| Metformin 500mg XR | Extended-release | Start or switch if stomach upset | Once daily, evening meal | 2,000mg (4 tablets) | [Metformin 500mg XR] |
| Metformin 850mg | Regular | Once-daily start or maintenance | 1–3 times daily with meals | 2,550mg (3 tablets) | [Metformin 850mg] |
| Metformin 1000mg | Regular | Maintenance with fewer tablets | 1–3 times daily with meals | 3,000mg (3 tablets) | [Metformin 1000mg] |
| Metformin 1000mg XR | Extended-release | Once-daily maintenance | Once daily, evening meal | 2,000mg (2 tablets) | [Metformin 1000mg XR] |
Swallow XR tablets whole. Do not crush, split or chew them, as this releases the full dose at once.
Editor note: replace each bracketed shop link with the live product URL and remove any strength DOC does not stock.
Starting dose and how it is increased
Doctors start low and go slow. Raising the dose gradually gives your stomach time to adjust and cuts nausea and diarrhoea.
A typical adult schedule with regular 500mg tablets:
- Week 1: 500mg once daily with breakfast or dinner
- Week 2: 500mg twice daily (breakfast and dinner)
- Week 3: 500mg with breakfast, 1,000mg with dinner
- Week 4 onwards: 1,000mg twice daily (2,000mg total), if needed and tolerated
With 850mg tablets, doctors usually start at 850mg once daily and add a dose every 1–2 weeks. With XR tablets, the start is 500mg once daily with the evening meal, raised by 500mg each week.
Your doctor checks your HbA1c about every 3 months and adjusts from there. Many people reach good control at 1,500–2,000mg a day.
Children aged 10 and over: start at 500mg or 850mg once daily, up to 2,000mg a day in 2–3 doses, under a specialist’s care.
Maximum daily dose of metformin
The maximum adult dose is 3,000mg a day for regular tablets and 2,000mg a day for XR tablets, if your kidneys are healthy.
| Tablet type | Max per day (adults) | How it is split |
|---|---|---|
| Regular (immediate-release) | 3,000mg | 3 doses with meals |
| Extended-release (XR) | 2,000mg | Once daily with evening meal |
| Children 10+ (regular) | 2,000mg | 2–3 doses with meals |
Some product labels, such as those used in the US, cap regular metformin at 2,550mg. Follow the limit on your own pack and your doctor’s instructions.
Above about 2,000mg, extra blood sugar benefit is small and side effects rise. If you are still above target at this level, your doctor will usually add a second medicine rather than push metformin higher.
Never take more than prescribed. A metformin overdose can cause lactic acidosis, a medical emergency.
Best time to take metformin
Take metformin with a meal or straight after one. Food reduces stomach upset, and timing doses with meals matches when your blood sugar rises.
| Dosing | When to take |
|---|---|
| Once daily (regular) | With breakfast or your evening meal |
| Twice daily | With breakfast and evening meal |
| Three times daily | With breakfast, lunch and evening meal |
| XR once daily | With your evening meal |
Take it at about the same times every day. If you have trouble with diarrhoea or nausea, ask your doctor about switching to XR.
During Ramadan: doses are usually moved to sahur and iftar, with the larger dose at iftar. Speak to your doctor before fasting so your dose can be planned safely.
Metformin dose and kidney function
Your kidneys clear metformin, so the safe dose falls as kidney function drops. Doctors check eGFR before starting and at least once a year.
| eGFR (mL/min/1.73m²) | Metformin dose |
|---|---|
| 60 or above | Normal dosing, up to the full maximum |
| 45–59 | Usually up to 2,000mg/day; check kidneys every 3–6 months |
| 30–44 | Max 1,000mg/day; starting new is generally not advised |
| Below 30 | Do not take metformin |
Metformin is also paused before and for 48 hours after scans with iodine contrast dye, and before major surgery. It is restarted once kidney function is confirmed stable.
Tell your doctor if you have liver disease, heart failure or drink alcohol heavily. These raise the risk of lactic acidosis.
Missed doses and side effects
If you miss a dose, take it with your next meal if you remember soon. If it is almost time for your next dose, skip the missed one. Never take two doses together to catch up.
Common side effects usually ease within 1–2 weeks:
- Nausea, stomach pain or bloating
- Diarrhoea
- Metallic taste
- Reduced appetite
Long-term use can lower vitamin B12. Your doctor may test your levels, especially if you notice tingling or numbness in your hands or feet.
Metformin alone rarely causes low blood sugar. The risk rises if you also take insulin or a sulfonylurea, skip meals or drink alcohol.
Get urgent medical help if you have signs of lactic acidosis: severe muscle pain, fast or difficult breathing, extreme tiredness, stomach pain with vomiting, or feeling cold and dizzy. Stop metformin and go to the nearest emergency department.
Get your metformin from DoctorOnCall
Refill your metformin online and get it delivered to your door, with every order checked by a registered pharmacist.
- Have a prescription? Upload it at checkout and choose your strength: [Metformin 500mg] · [Metformin 500mg XR] · [Metformin 850mg] · [Metformin 1000mg] · [Metformin 1000mg XR]
- No prescription or need a dose review? [Consult a doctor online] in minutes. They can assess your diabetes, review your dose and issue an e-prescription.
- Taking it long term? Ask our pharmacists about switching to XR or managing side effects.
Editor note: confirm the prescription upload and e-consult flow wording against the live checkout before publishing.
Frequently asked questions
Is metformin 1000mg a high dose?
No. 1,000mg is a common single dose, often taken twice daily for 2,000mg a day. It is well below the 3,000mg daily maximum for regular tablets.
What is metformin HCl 500mg?
Metformin HCl (hydrochloride) is the salt form in nearly all metformin tablets. Metformin HCl 500mg and metformin 500mg are the same medicine.
Can I take metformin 1000mg once a day?
Yes, if it is the XR version, taken with your evening meal. Regular 1000mg tablets are usually split across two meals.
Is metformin better taken in the morning or at night?
With meals is what matters. XR works best with the evening meal. Regular tablets are taken with whichever meals your doctor sets.
Can I take metformin on an empty stomach?
It is not recommended. Taking it without food makes nausea and diarrhoea more likely.
How long does metformin take to work?
Blood sugar starts to fall within days. The full effect on HbA1c shows after about 2–3 months at a steady dose.
Can I drink alcohol on metformin?
Keep alcohol light and never drink heavily. Alcohol raises the risk of low blood sugar and lactic acidosis.
Do I need a prescription to buy metformin in Malaysia?
Yes. You can upload your prescription or get one through an online consultation at DoctorOnCall.
