Metformin remains the most prescribed medication for type 2 diabetes worldwide. Doctors often start patients on this simple pill because it works well, has decades of safety data, and costs very little. Millions take it daily to keep blood sugar under control.
Unlike newer drugs that cost hundreds or thousands per month, metformin rarely creates financial stress. Still, patients want to know exactly what insurance pays for metformin and how much they will actually spend out of pocket in 2025.
This guide explains coverage across every major insurance type, typical copays, and why metformin almost never gets denied.
What Is Metformin and Why Is It So Common?
Metformin belongs to the biguanide class of drugs. It lowers blood sugar by reducing liver glucose output and improving insulin sensitivity in muscles. Most people start at 500 mg once or twice daily and increase slowly to avoid stomach upset.
It comes in immediate-release tablets, extended-release (ER) tablets, and a low-cost liquid form. The ER version often causes fewer side effects and only needs one pill at night. Brand names include Glucophage, Glumetza, and Fortamet, but generics dominate the market.
Different Forms and Typical Costs Without Insurance
Generic metformin is one of the cheapest medicines available. Immediate-release 500 mg tablets cost $4–$10 for a 90-day supply at major discount programs. Extended-release versions run $10–$40 for 90 days.
Even the most expensive brand-name versions rarely exceed $300 monthly. Most people pay less than $20 total per year when using generics and discount cards.
What Insurance Pays for Metformin? The Direct Answer
Almost every insurance plan in the United States pays for metformin in 2025. It sits on Tier 1 (lowest copay) of nearly all formularies because it is generic, proven, and recommended as first-line therapy by the American Diabetes Association.
Medicare, Medicaid, commercial plans, and marketplace coverage all include it with $0–$10 copays. Prior authorization is almost never required.
How to Confirm Your Specific Coverage for Metformin
Step 1: Check Your Plan’s Drug Formulary Online
Log into your insurance portal or app. Search for “metformin,” “metformin ER,” or “Glucophage.” It will show the tier and exact copay amount for 30-day or 90-day fills.
Step 2: Look at Preventive Drug Lists
Many plans place metformin on a $0 copay preventive list if you have diabetes or prediabetes. This applies even before you meet your deductible.
Step 3: Choose Preferred Pharmacy or Mail Order
Using in-network pharmacies like CVS, Walgreens, or mail-order through OptumRx or Express Scripts drops cost to the lowest tier. Some plans waive copays completely at preferred locations.
Step 4: Ask About Quantity Limits or Form Preferences
Most plans allow 90–180 day supplies at once for chronic conditions. A few prefer the ER version and may charge more for immediate-release if not justified.
Coverage and Cost by Insurance Type in 2025
| Insurance Type | Tier Level | Typical Copay (30-day) | Typical Copay (90-day) | Notes 2025 |
|---|---|---|---|---|
| Medicare Part D | Tier 1 | $0–$10 | $0–$20 | Often $0 under preventive list |
| Medicare Advantage | Tier 1 | $0–$5 | $0–$10 | Many plans $0 after deductible |
| Medicaid | Tier 1 | $0–$4 | $0–$4 | $0 in most states |
| Commercial/Employer Plans | Tier 1 | $0–$10 | $0–$20 | $0 at preferred pharmacies |
| Marketplace (ACA) Silver+ | Tier 1 | $0–$10 after deductible | $0–$25 | Preventive list covers prediabetes |
| Tricare / VA | Covered | $0–$12 | $0 | VA supplies free to veterans |
Why Metformin Almost Never Faces Coverage Issues
The FDA first approved metformin in 1995, and generics hit the market in 2002. With no patent protection left, prices collapsed. Insurance companies love it because it prevents expensive complications like heart attacks and kidney failure.
Every major medical guideline lists it as the starting drug for type 2 diabetes. Denying coverage would go against standard care and trigger appeals that insurers always lose.
Extra Benefits Many Plans Offer in 2025
Some plans now cover metformin for prediabetes without a diabetes diagnosis. The Affordable Care Act labels it a preventive drug, meaning $0 copay even before deductible in Silver, Gold, and Platinum marketplace plans.
Large employers often include free glucose test strips and meters when you fill metformin. Several states expanded Medicaid to cover it for PCOS and fertility treatment off-label.
When You Might Pay More Than Expected
Brand-name Glucophage XR or Glumetza costs $200–$400 monthly and sits on higher tiers. Your doctor must prove the generic ER version caused severe side effects to get brand approval.
A few plans limit you to one tablet strength unless justified. Switching from 500 mg twice daily to 1000 mg ER once daily usually solves this at no extra cost.
Savings Programs Even If You Have Insurance
Walmart, Costco, and Kroger sell 180 tablets of 500 mg metformin for $4–$10 without using insurance. GoodRx coupons drop ER versions to $12–$25 for 90 days. These cash prices often beat insured copays.
Mark Cuban’s Cost Plus Drug Company sells 500 mg tablets for $4.20 and ER 500 mg for $6.90 per month including shipping. No insurance needed.
Off-Label Uses and Insurance Coverage
Doctors prescribe metformin for PCOS, gestational diabetes, and weight loss in non-diabetics. Most plans still cover it because the drug itself is approved and cheap.
Prior authorization may appear for non-diabetes diagnoses in strict plans. A simple letter of medical necessity from your doctor fixes this 99% of the time.
Comparing Metformin to Newer Diabetes Drugs
| Drug | Average Monthly Cost With Insurance | Tier Level | Prior Auth Needed? |
|---|---|---|---|
| Metformin | $0–$10 | Tier 1 | Almost never |
| Jardiance | $400–$600 | Tier 3 | Usually |
| Ozempic | $25–$300 | Tier 3 | Yes |
| Trulicity | $100–$800 | Tier 3 | Yes |
| Januvia | $400–$550 | Tier 3 | Sometimes |
Tips for the Lowest Possible Cost
Ask your doctor to write for 90–180 day supplies.
Switch to the extended-release version if stomach issues appear.
Use mail-order pharmacy for automatic refills and free shipping.
Combine with free ADA diabetes education classes many plans cover.
Summary
What insurance pays for metformin is simple: nearly every plan in America covers it fully or with tiny copays in 2025. It sits on Tier 1 with $0–$10 cost for most patients, and prior authorization is extremely rare. Medicare, Medicaid, and private plans all treat it as essential first-line therapy. Cash prices stay so low that many people pay less without insurance than with high-deductible plans.
FAQ
Does Medicare Part D cover metformin in 2025?
Yes, on Tier 1 with $0–$10 copay. Many plans list it as $0 preventive drug even before the deductible is met.
Is metformin free with insurance?
Yes for millions of patients. Preventive lists, Medicaid, and many employer plans charge $0 at preferred pharmacies.
Why do some people still pay $30–$50 for metformin?
They may fill brand-name versions or use out-of-network pharmacies. Switching to generic ER at an in-network location drops it to $0–$10.
Does insurance cover metformin for PCOS or prediabetes?
Yes in most cases. The drug itself is Tier 1, so coverage applies even off-label. A few plans want a short prior auth letter.
Is the extended-release version covered the same as regular?
Yes, both sit on Tier 1. Most plans prefer ER and may charge slightly more for immediate-release if not medically justified.
Can I get a 90-day supply of metformin through insurance?
Yes, almost every plan allows 90–180 day fills for chronic conditions at lower or equal copay per month. Mail-order often makes it free.
Dr. Hamza is a medical content reviewer with over 12+ years of experience in healthcare research and patient education. He specializes in evidence-based health information, medications, and chronic conditions. His reviews are grounded in trusted medical sources and current clinical guidelines to ensure accuracy, transparency, and reliability. Content reviewed by Dr. Hamza is intended for educational purposes and is not a substitute for professional medical advice.