What Is the 30-Month Coordination Period for Medicare?

The 30-month coordination period for Medicare is the window that begins the first month you become eligible for Medicare because of End-Stage Renal Disease, during which your employer Group Health Plan pays your medical bills first and Medicare pays second. It lasts exactly 30 months, and it applies to all your covered healthcare during that window, not only kidney treatment. When the 30 months run out, the order flips: Medicare becomes primary and your group plan drops to secondary.¹

How the Payment Order Works

During the 30 months, you submit claims to your group plan first. The plan pays up to the limits of its benefits, and Medicare then covers allowable costs the plan didn’t fully pay.¹ Tell every provider you see about both coverages so claims are billed in the right order.

Your group plan cannot treat you differently because of your kidney disease. It cannot reduce your benefits, deny coverage, drop you from enrollment, or charge higher premiums based on your ESRD diagnosis or need for dialysis, and this protection runs for the entire coordination period.²

Who the Period Applies To

The 30-month period applies if you become eligible for Medicare specifically because of ESRD and you also have Group Health Plan coverage. Unlike the coordination rules that apply when Medicare eligibility comes from age or disability, the ESRD version has no employer-size threshold. It runs the same way whether your employer has five workers or five thousand.³

It also doesn’t matter whether you’re still working. Coverage through a current job, retiree health benefits, or COBRA continuation coverage all trigger the 30-month window in which your group plan pays first.³

COBRA deserves special attention. When you have COBRA and become Medicare-eligible through ESRD, COBRA pays first during the 30 months. That reverses the usual rule, where COBRA pays second to Medicare for people who qualify through age or disability. There’s a catch: federal law lets a group plan terminate COBRA when you become entitled to Medicare. If your COBRA ends for that reason, Medicare becomes your primary payer immediately for the rest of the coordination period.¹

When the Clock Starts

The 30 months start the first month you become eligible for Medicare because of ESRD. CMS uses the month you could have enrolled, not the month you actually filed. Delaying your Medicare application doesn’t pause or extend the clock.⁴

For most people starting dialysis, Medicare coverage begins on the first day of the fourth month after dialysis treatments start. That three-month waiting period means the 30-month coordination period also starts in that fourth month.⁵

Two situations waive the waiting period and start the clock sooner:

You begin a self-dialysis training program at a Medicare-approved facility, and a physician expects you to complete the program and dialyze at home. Medicare eligibility and the 30-month clock start immediately.⁶
You receive a kidney transplant. Medicare coverage can start the month you’re admitted to a Medicare-approved hospital for the transplant or for pre-transplant care.⁵

If You Already Have Medicare Through Age or Disability

The answer depends on who was paying first before your ESRD diagnosis. If your group plan was already the secondary payer (because your employer had fewer than 20 employees for age-based Medicare, or fewer than 100 employees for disability-based Medicare), Medicare stays primary after your ESRD diagnosis. The plan can’t start treating you differently because of the kidney disease, but the payment order doesn’t change.⁷

If your group plan was the primary payer before ESRD (because you were actively working for a larger employer), the 30-month ESRD coordination period applies. Your group plan stays primary for 30 months from when you first become eligible for Medicare based on ESRD, and Medicare remains secondary during that window.⁷

People who already have Medicare through age or disability don’t have to wait three months for dialysis coverage. Medicare pays for ESRD-related treatment right away.⁵

Should You Enroll in Part B During the Period?

You’re not required to enroll in Medicare Part B during the coordination period, and the decision depends on how well your group plan already covers you.⁸ If your group plan covers most of your costs with little out-of-pocket, delaying Part B saves you the monthly premium. The standard Part B premium for 2026 is $202.90 per month, more than $2,400 a year.⁹

If you qualify for Medicare because of ESRD, you can sign up for Part B later without paying a late enrollment penalty.⁸ That’s a real advantage over the general Medicare rules, where waiting typically adds a 10% surcharge for every full year of delay, lasting as long as you have Part B.¹⁰

If your group benefits are reduced or your coverage ends during the 30 months, enroll in Part B as soon as possible. You have an eight-month Special Enrollment Period starting the month after your group coverage or employment ends, whichever comes first.¹¹ Miss that window and you could be left without adequate coverage.

What Happens When the 30 Months End

Once the 30 months have passed, Medicare automatically becomes your primary payer for all Medicare-covered services, as long as you’re enrolled. Your group plan shifts to secondary and picks up what Medicare leaves, including services Medicare doesn’t cover at all. The transition happens without any paperwork on your part.³

If you put off Part B during the coordination period, this is the moment to sign up. You want both Part A and Part B in place before the clock runs out so there’s no gap where you owe the full cost of services your group plan only partially covers as a secondary payer.

When a New 30-Month Period Starts

A transplant doesn’t always work permanently. If yours fails and you return to dialysis, you get a brand-new 30-month coordination period. There’s no three-month waiting period the second time. Your ESRD-based Medicare entitlement restarts the month you resume dialysis, and a fresh 30-month clock begins from that point.⁴

The same restart applies if your ESRD-based Medicare ended (because you went 12 months without dialysis, or because 36 months passed after a successful transplant) and you later need dialysis again. You get a new Medicare enrollment based on ESRD and a new 30-month coordination period with your group plan.¹²

1
eCFR. 42 CFR Part 411 Subpart F – Special Rules: Individuals Eligible or Entitled on the Basis of ESRD, Who Are Also Covered Under Group Health Plans
2
Office of the Law Revision Counsel. 42 US Code 1395y – Exclusions From Coverage and Medicare as Secondary Payer
3
Social Security Administration. Medicare Information
4
CMS. Medicare Secondary Payer ESRD Introduction
5
Medicare. Medicare Coverage of Kidney Dialysis and Kidney Transplant Benefits
6
SSA. Date of ESRD Medicare Entitlement Based on Self-Dialysis Training
7
eCFR. 42 CFR 411.163 – Coordination of Benefits: Dual Entitlement Situations
8
Medicare. End-Stage Renal Disease (ESRD)
9
CMS. 2026 Medicare Parts A and B Premiums and Deductibles
10
Medicare. Avoid Late Enrollment Penalties
11
SSA. Special Enrollment Period (SEP)
12
CMS. End-Stage Renal Disease (ESRD)