How to Take Metformin: Side Effects, Dosage
How to take metformin: dosage guidelines, common side effects, and important information for managing type 2 diabetes.
Not medical advice. Speak with a healthcare professional before using any medication.
Reviewed by:
Updated Feb, 15
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Information sourced from FDA-approved prescribing information and peer-reviewed medical references.
How to Take Metformin
How to Take Metformin
Per FDA-approved prescribing information, the following reflects standard dosing guidance for metformin. Follow your prescriber's instructions, which may differ from the general information below.
- Per FDA-approved prescribing information, the usual starting dose for adults is 500 mg once or twice daily with meals, or 850 mg once daily with a meal. Your clinician may increase your dose gradually every 1–2 weeks to improve blood sugar control.
- Per FDA-approved prescribing information, if prescribed the extended-release (ER) version: take it once daily with your evening meal. Swallow tablets whole — do not crush or split. It is normal to see the tablet shell in your stool.
- Per FDA-approved prescribing information, take metformin with food: a meal or substantial snack helps reduce stomach upset.
- Per FDA-approved prescribing information, the usual maximum daily dose is: 2000 mg for most ER formulations and 2550 mg for immediate-release, divided with meals as directed by your clinician.
- Per FDA-approved prescribing information, if you miss a dose: take it when you remember unless it is almost time for the next dose. Do not double up.
- Maintain adequate fluid intake while taking this medication.
- Per FDA-approved prescribing information, take it at the same times each day to help maintain consistent blood sugar levels.
Warnings Before Taking Metformin
BLACK BOX WARNING (Per FDA-approved prescribing information): Lactic acidosis — a rare but serious and potentially fatal buildup of lactic acid in the blood has been reported with metformin use. Risk is higher in patients with renal impairment, hepatic impairment, congestive heart failure, or excessive alcohol intake. Discontinue immediately if lactic acidosis is suspected.
Per FDA-approved prescribing information, tell your doctor about kidney, liver, or heart problems, as these can affect dosing and safety.
Per FDA-approved prescribing information, avoid excessive alcohol, which raises the risk of lactic acidosis.
Per FDA-approved prescribing information, inform your clinician before contrast dye imaging; metformin may need to be temporarily discontinued.
Per FDA-approved prescribing information, discuss pregnancy or breastfeeding with your clinician before use.
Metformin Side Effects
common
Mild
Gastrointestinal Upset
BLACK BOX WARNING: Per FDA-approved prescribing information, lactic acidosis is a rare but serious risk associated with metformin. Symptoms may include nausea, vomiting, abdominal pain, and muscle pain. Seek emergency care if these occur with unusual tiredness or difficulty breathing.
Per FDA-approved prescribing information, nausea, stomach discomfort, or cramping are among the most common adverse effects of metformin, particularly during the first weeks of treatment or with dose increases.
Per FDA-approved prescribing information. If symptoms persist or worsen, stop use and consult a healthcare provider.
Normally lasts for:
2–6 hours
common
Mild
Diarrhea
Per FDA-approved prescribing information, metformin can increase bowel activity, leading to loose stools, particularly when doses are increased too quickly.
Per FDA-approved prescribing information. If symptoms persist or worsen, consult a healthcare provider.
Normally lasts for:
4–12 hours
common
Mild
Loss of Appetite
Per FDA-approved prescribing information, some patients experience a reduced desire to eat with metformin use.
Per FDA-approved prescribing information. If symptoms persist or worsen, consult a healthcare provider.
Normally lasts for:
1–3 hours
uncommon
Mild
Metallic Taste
Per FDA-approved prescribing information, a temporary metal-like taste in the mouth has been reported with metformin use.
Per FDA-approved prescribing information. If symptoms persist or worsen, consult a healthcare provider.
Normally lasts for:
30–60 minutes
rare
Moderate
Vitamin B12 Lowering
Per FDA-approved prescribing information, long-term use of metformin can decrease vitamin B12 absorption. Periodic monitoring of B12 levels may be recommended by your clinician.
Per FDA-approved prescribing information. If symptoms persist or worsen, consult a healthcare provider.
Normally lasts for:
No effect from a single dose
uncommon
Mild
Mild Fatigue
Per FDA-approved prescribing information, a small number of patients report fatigue or low energy when initiating metformin therapy.
Per FDA-approved prescribing information. If symptoms persist or worsen, consult a healthcare provider.
Normally lasts for:
2–6 hours
Contact Us for a Personalized Care Plan
Have questions about compounding? Contact Voshell's Pharmacy — we prepare patient-specific medications pursuant to valid prescriptions from your licensed prescriber.
What If You Forgot to Take Metformin
What If You Forgot to Take Metformin?
Per FDA-approved prescribing information, if you miss a dose, take it as soon as you remember unless it is almost time for your next scheduled dose.
- Per FDA-approved prescribing information, if it is close to the next dose: skip the missed one and return to your usual schedule.
- Do not double up or take extra doses to make up for a missed one.
If you are unsure or missing doses becomes frequent, contact your clinician or pharmacist for guidance on your dosing schedule.
What If You Took Too Much Metformin
What If You Took Too Much Metformin by Accident?
Contact Poison Control at 1-800-222-1222 right away. If symptoms of lactic acidosis are present — including nausea, muscle pain, or difficulty breathing — seek emergency medical care immediately.
- Do not take additional doses until you have spoken with Poison Control or a clinician.
- If symptoms of lactic acidosis develop (nausea, vomiting, muscle pain, weakness, difficulty breathing, unusual drowsiness, or stomach discomfort), seek emergency medical care immediately.
- Keep this and all medications out of reach of children.
How Much Does Metformin Cost
Cost of Metformin With Insurance
With most U.S. insurance plans, metformin is typically placed on a low-tier formulary due to its availability as a generic medication.
Many plans place it on a preferred generic tier with low copay amounts.
Some insurance plans may offer it at no copay, particularly for diabetes management programs.
Extended-release versions may cost more than immediate-release under some plan designs.
Actual cost depends on your specific plan's formulary, tier placement, and dispensing pharmacy. Contact your insurer or pharmacist for current pricing information.
How Much Does Metformin Cost without Insurance
Cost of Metformin Without Insurance
Metformin is available as a generic medication at many U.S. pharmacies. Cash-pay prices vary by pharmacy, dose, and quantity.
- Immediate-release tablets (500 mg or 1000 mg) are available at many retail pharmacies for a 30-day supply; prices vary by location.
- Extended-release (ER) versions are generally priced higher than immediate-release at cash-pay rates.
- Discount programs offered by pharmacy chains and third-party services may reduce out-of-pocket costs.
Contact your local pharmacy for current cash pricing. Prices are subject to change and vary by location.
Resources:
https://medlineplus.gov/druginfo/meds/a696005.html
https://www.fda.gov/drugs/postmarket-drug-safety-information-patients-and-providers/metformin-containing-drugs
https://www.nhs.uk/medicines/metformin/
https://www.mayoclinic.org/drugs-supplements/metformin-oral-route/description/drg-20067074
https://www.ncbi.nlm.nih.gov/books/NBK518983/
