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PlainMedicare

Is Janumet (metformin hydrochloride / sitagliptin phosphate) covered by Medicare Part D?

4,788 of 5,052 Medicare Part D plan offerings (94.8%) list Janumet on their 2026 formulary, most often on tier 3; 0.3% of the formularies that cover it require prior authorization. Part D spending on it was $1.1 billion in 2024 for at least 159,321 people: what plans and patients paid at the pharmacy, before manufacturer rebates (CMS Part D Spending by Drug).

Plans that cover it
94.8%
4,788 of 5,052 offerings; the median drug: 76%
Usual tier
Tier 3
from tier 1 to tier 6
Prior authorization
0.3%
of formularies that cover it; the median drug: 1%
Quantity limits
93.7%
of formularies that cover it; the median drug: 30%

Source: CMS Part D formulary file, 2026 second quarter: the formularies in use in 2026. A plan's 2027 formulary can differ; check your own plan's coverage in Medicare Plan Finder.

What does it cost under Part D in 2027?

A negotiated price
Medicare negotiated a lower price for Janumet, in effect from January 1, 2027: $80 for a 30-day supply, against a list price of $526 (2024); CMS gives one figure for Janumet and Janumet XR together. Where your share is a percentage of the drug's price, it is a percentage of the lower price; a flat copay stays as your plan sets it.
Your yearly cap in 2027
Out-of-pocket spending on covered Part D drugs stops at $2,400 in 2027 ($2,100 in 2026); after that, you pay nothing for covered drugs for the rest of the year.
The deductible
A plan's drug deductible is at most $700 in 2027 ($615 in 2026); many plans charge less or none.

Source: CMS, Announcement of calendar year 2027 Part D parameters; Medicare.gov, “How much does Medicare drug coverage cost?”; CMS, “Selected drugs and negotiated prices” (read Oct. 7, 2026).

How much does Medicare spend on it?

Part D spending by year

2020$1.2 billion
2021$1.2 billion
2022$1.2 billion
2023$1.2 billion
2024 (latest)$1.1 billion

159,321 people filled it under Part D in 2024, in 1,126,872 claims. The amounts are what plans and patients paid at the pharmacy, before manufacturer rebates.

Source: CMS Medicare Part D Spending by Drug, 2020 to 2024 (published June 2026). Row used: Janumet (Sitagliptin Phos/Metformin HCl), Janumet XR (Sitagliptin Phos/Metformin HCl).

Which forms and strengths are counted?

  • 24 hour metformin hydrochloride 1000 mg / sitagliptin phosphate 100 mg extended-release oral tablet
  • 24 hour metformin hydrochloride 1000 mg / sitagliptin phosphate 50 mg extended-release oral tablet
  • 24 hour metformin hydrochloride 500 mg / sitagliptin phosphate 50 mg extended-release oral tablet
  • metformin hydrochloride 1000 mg / sitagliptin phosphate 50 mg oral tablet
  • metformin hydrochloride 500 mg / sitagliptin phosphate 50 mg oral tablet

What else should you check?

Data, not medical advice. Coverage is the share of plan formularies listing the drug; your plan's formulary, tier and pharmacy decide what you pay.