Guide

Medicare vs. employer health insurance: when to switch?

Turning 65 while you're still working is one of the most common — and most expensive-to-get-wrong — Medicare decisions. Here's how to compare your employer plan with Medicare without the sales pitch.

Desk with employer insurance card, Medicare card, calculator, and stethoscope

The one number that changes everything

Before you compare premiums or networks, find out how many employees your company has. That single number decides whether Medicare or your employer plan pays first.

20+ employees: your employer plan is primary. You can usually delay Part B without penalty and sign up later through a Special Enrollment Period when you retire.
Under 20 employees: Medicare is primary. If you don't take Part B at 65, your employer plan can pay as if Medicare already paid — and leave you responsible for the rest.

Side-by-side comparison

Factor	Employer plan	Medicare
Monthly cost	Often subsidized by employer; may include dependents.	Part A is usually free; Part B is ~$185/mo in 2026; Part D and Medigap add cost.
Network	Tied to your employer's chosen plan and carrier.	Original Medicare is accepted nationwide by most doctors/hospitals.
Out-of-pocket max	ACA caps annual out-of-pocket costs.	Original Medicare has no cap; Medigap fills most gaps, or Advantage plans add a cap.
Drug coverage	Included in most employer plans.	Requires a separate Part D plan or Medicare Advantage plan with drug coverage.
Portability	Ends when employment ends (COBRA is temporary and not creditable for Part B).	Follows you for life once enrolled.

The HSA trap

The moment you enroll in any part of Medicare — including premium-free Part A — you must stop contributing to a Health Savings Account. Part A can be backdated up to six months, so stop HSA contributions at least six months before you plan to enroll or file for Social Security.

The COBRA warning

COBRA is not creditable coverage for delaying Part B. If you retire at 66 and go on COBRA for 18 months, your 8-month Part B Special Enrollment Period started the day your active employment ended — not when COBRA ends. Miss it and you'll owe a lifetime late penalty and wait for the General Enrollment Period.

When Medicare usually wins

Your employer plan is expensive or has a narrow network.
You see specialists who aren't in the employer plan.
You plan to retire within the next year or two.
Your employer has fewer than 20 employees.

When keeping employer coverage usually wins

Your employer heavily subsidizes premiums.
You have dependents who need the employer plan.
Your doctors are all in-network and you're happy with the plan.
You plan to keep working for several more years.

What to do this month

✅ Confirm employer size (20+ or under 20) in writing.
✅ Request your Part D creditable-coverage notice from HR.
✅ Stop HSA contributions at least 6 months before enrolling.
✅ Compare total annual cost, not just premiums.

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Educational only — not legal or tax advice. Employer size rules, HSA rules, and enrollment windows can change; confirm with your HR/benefits team, Social Security, or a licensed agent before acting.