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Pre-Existing Condition Medicare Supplement Insurance: The Look-Back, the Wait and Who Skips Both

Reviewed by Russell Noga, Licensed Medicare Insurance Broker (all 50 states) — Last updated November 10, 2026

Medicare Supplement insurance can delay coverage of a pre-existing condition for up to six months, and that delay is cut by one month for every month of prior creditable coverage you had with no break longer than 63 days. When you buy under a guaranteed issue right, no waiting period applies at all, and Original Medicare keeps paying its share of your care either way.

2027 by the Numbers

6 months

longest pre-existing condition waiting period federal law allows on a Medigap policy

63 days

longest break in prior coverage that still counts toward shortening the wait

38 states

require at least one Medigap policy for people under 65 with disabilities (KFF)

12 + DC

states that do not require Medigap sales to people under 65 (KFF)

Pre-existing condition rules for Medigap trip people up because two different six-month periods are involved, one looking backward from your start date and one looking forward. Mix them up and it is easy to think a condition is excluded when it is not, or the reverse.

This guide puts real dates on both clocks, shows how prior coverage erases the wait month by month, and explains what you still owe while a condition is excluded. For the broader question of when an insurer can refuse an application, see can Medicare Supplement plans deny coverage.

✔ Licensed in all 50 states
✔ Based on CMS 2027 data
✔ Free plan comparison

Key Highlights

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The look-back checks for advice or treatment in the six months before the policy starts.

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The waiting period can last up to six months after it starts, minus credit for prior coverage.

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Original Medicare still pays its normal share for an excluded condition.

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Under-65 protections vary widely by state, and some states require no sales at all.

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Two Six-Month Clocks That Get Mixed Up

The look-back (before)

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Covers roughly the six months before your policy’s effective date

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Asks whether a doctor gave advice or recommended or provided treatment

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Decides which conditions count as pre-existing

The waiting period (after)

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Covers up to six months after your policy’s effective date

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During it, the policy may not pay toward that one condition

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Shrinks with prior creditable coverage and disappears under guaranteed issue

The look-back definition comes from the model rules most states adopt from the National Association of Insurance Commissioners. A condition you had years ago but were not treated for in that six-month span is generally not pre-existing for this purpose. Your policy wording controls, so read the pre-existing condition section of the outline of coverage.

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A Dated Example: A Policy Starting February 1, 2027

Picture someone whose Medigap policy takes effect February 1, 2027, who had no other health coverage before Medicare and who saw a cardiologist in October 2026.

Date range Which clock What it means here
August 1, 2026 to January 31, 2027 Look-back The October cardiology visit falls inside, so the heart condition is pre-existing
February 1 to July 31, 2027 Waiting period The policy may decline to pay its share of heart-related bills
August 1, 2027 onward Normal coverage The policy pays for the heart condition like any other covered care
Any date Unrelated care A broken wrist or the flu is covered from February 1

Illustration using the federal maximum. Prior creditable coverage or a guaranteed issue right would shorten or remove the wait.

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Counting Creditable Coverage Month by Month

Each month of prior health coverage takes one month off the wait, as long as that coverage ended no more than 63 days before the Medigap policy began.

Months of prior creditable coverage Longest possible wait left
0 6 months
2 4 months
4 2 months
6 or more None

Coverage that usually counts

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An employer or union group health plan, including COBRA

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Medicare Part A and Part B, or a Medicare Advantage plan

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Medicaid

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Military coverage such as TRICARE

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An individual health insurance policy

What You Still Owe While a Condition Is Excluded

A waiting period does not mean the condition goes uncovered. Original Medicare pays first, as it always does, and the Medigap policy simply holds back its part of that one condition’s bills. Our math shows the exposure for a member with Plan G in 2027.

$2,000

20% Part B coinsurance on $10,000 of outpatient treatment for the excluded condition

$292

projected 2027 Part B deductible, which a Plan G member pays in any case

$1,736

Part A hospital deductible in 2026; the 2027 amount is still pending from CMS

Worth knowing: New conditions that first appear after the policy starts are never subject to a pre-existing condition waiting period. The exclusion only reaches conditions caught by the look-back.

Moments When the Insurer Cannot Use Your History

No waiting period and no health pricing

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Buying under a federal guaranteed issue right, such as a Medicare Advantage plan leaving your area

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Using the Medicare Advantage trial right within its first 12 months

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Buying during your six-month Medigap open enrollment period with at least six months of prior creditable coverage

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Living in Connecticut or New York, where people 65 and older have year-round guaranteed issue

During the six-month Medigap open enrollment period an insurer cannot refuse you or charge more because of health, but if you had little or no prior coverage, it can still apply a shortened wait. The full list of protected events is on our guaranteed issue Medicare Supplement page.

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Under 65 With a Disability: State Rules Decide

Federal Medigap open enrollment protections are written for people 65 and older. For younger people on Medicare because of a disability, end-stage renal disease or ALS, the state sets the rules.

State approach Number of states What it means for health history
Require at least one Medigap policy for under-65 enrollees during an initial window 38 Insurers must accept you in that window regardless of conditions
Require all plan types for that group 27 of those 38 Wider choice of plan letters
No requirement to sell to under-65 enrollees 12 plus DC Insurers may decline or may not offer policies at all
Explicitly require sales to people with ESRD 28 Kidney failure cannot be used to refuse you in the protected window

Source: KFF review of state Medigap requirements, 2026. California, Massachusetts, Vermont and Nebraska explicitly exclude people with ESRD from their under-65 requirement.

Price check: Several states that require under-65 sales still let insurers charge younger enrollees much higher premiums. Compare quotes before assuming a policy is affordable.

Filling Out the Health Section Without Surprises

1

List dates, not just diagnoses Write down when each condition was diagnosed, last treated and last changed.

2

Pull your medication list Insurers often check prescription histories, and a drug can point to a condition.

3

Check whether a protected window applies If it does, the health questions may not apply to you at all.

4

Answer every question fully A policy issued on inaccurate answers may be cancelled or a claim denied later.

5

Keep a copy of the application It shows exactly what you disclosed if a claim is ever questioned.

Bottom Line

The Bottom Line

A pre-existing condition can delay Medigap payments for up to six months, but prior creditable coverage shortens that wait and guaranteed issue rights erase it. Original Medicare keeps paying throughout, and anyone under 65 should check state rules first because they vary the most.

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Frequently Asked Questions

➤ Do Medicare Part A and Part B have any pre-existing condition exclusions?

No. Original Medicare covers medically necessary care for any condition from the day your coverage begins. Exclusions only come into play in the separate Medigap policy.

➤ How far back does a Medigap insurer look for a pre-existing condition?

Under the model rules most states use, the look-back is the six months before the policy starts. Advice or treatment in that span can make a condition pre-existing.

➤ Can my premium be higher because of a condition during my Medigap open enrollment period?

No. During that six-month window the insurer must charge you the same as someone in good health, although a short wait can still apply if you lacked prior coverage.

➤ Does a Medicare Advantage plan count as creditable coverage for Medigap?

Yes. Months in a Medicare Advantage plan count toward reducing the waiting period, as long as the gap before the Medigap policy starts is 63 days or less.

➤ Is a condition controlled by medication still considered pre-existing?

Usually yes, if you received treatment such as a prescription during the look-back period. Stable control does not by itself remove the condition from that definition.

➤ Does the waiting period apply to a problem diagnosed after my policy starts?

No. Only conditions caught by the look-back can be excluded. Anything that first shows up after the effective date is covered right away.

➤ Will choosing a different plan letter avoid the waiting period?

No. The same pre-existing condition rules apply to every standardized plan letter. Prior coverage and guaranteed issue rights are what change the outcome.

➤ If I am under 65 and on disability, can an insurer refuse me because of my condition?

It depends on your state. Most states require at least one policy in an initial window, but 12 states and DC do not require any sales to people under 65.

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☎ 1-855-398-0716

TTY users 711  |  Mon–Fri: 5am–7pm, Sat–Sun: 7am–4pm CT

No obligation to enroll

Find & Compare Plans Online

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Mon-Fri: 8am-9pm ET

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