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What is Medigap (Medicare Supplement insurance)?

Medigap is a private policy that pays the share Original Medicare leaves you, and every plan letter covers the same things at any company.

Updated September 3, 2026 · 3 min read · by Gerino Alejos


Illustration of the word Medigap above a map of the United States, a stethoscope, a Medicare card and a cake with 65 candles.
A private policy that pays the share Original Medicare leaves you. Standardized by law, priced by the company.
Key points
  • Medigap, also called Medicare Supplement insurance, is a private policy that pays bills Original Medicare leaves for you.
  • Original Medicare covers about 80 percent of most services, and nothing caps the other 20 percent you owe.
  • For six months after your Part B starts, no company in Texas can turn you down or charge you more for your health history.

Medigap, also called Medicare Supplement insurance, is a private policy that pays costs Original Medicare leaves for you. Original Medicare is the government coverage, Part A for hospital stays and Part B for doctor visits. It solves one problem.

The problem it solves: the 20 percent with no cap

Original Medicare covers about 80 percent of most services once you meet the Part B deductible, the amount you pay yourself before Medicare starts paying. The other 20 percent is yours, and there is no limit on it.

On a routine office visit, your 20 percent is small. On a $50,000 hospital stay, your 20 percent is $10,000.

A Medigap policy pays that share for you, so your costs become predictable. See which gaps a supplement fills.

Why every Plan G is identical by law

Medigap plans are labeled by letter, and federal law sets what each letter covers. A Plan G from one company covers exactly the same things as a Plan G from any other company.

So there is no fine print to compare. There is no network to check, no list of doctors and hospitals under contract, and no formulary, the list of drugs a plan pays for.

Since the coverage is identical, you are comparing price, the company's record on rate increases, and its service. See why identical plans cost different amounts.

How it works day to day

  1. You see any doctor in the country who takes Medicare.
  2. The doctor's office bills Medicare.
  3. Medicare pays its share and sends the rest to your Medigap company on its own.
  4. The supplement pays its share.
  5. With a plan that fills the most gaps, you often see no bill at all.

There are no networks and no referrals, the permission one doctor gives you to see another. There is very little prior authorization, where the plan approves care before you get it. That simplicity is the main thing you are buying. See using Medigap with any doctor.

What it does not include

  • Prescription drugs. You need a separate Part D plan, the part of Medicare that pays for medicine at the pharmacy.
  • Dental, vision and hearing. Medicare does not cover these, so there is nothing for the supplement to pay.
  • Long term custodial care, help with daily tasks like bathing, dressing and eating.
  • Anything else Medicare itself does not cover.

A supplement fills gaps in what Medicare covers. It cannot pay for something Medicare never covered. See what Medigap does not cover.

You cannot have Medigap and Medicare Advantage at once

Medigap pairs only with Original Medicare. You cannot hold a supplement and a Medicare Advantage plan at the same time. A Medicare Advantage plan is a private plan that changes how you receive your Medicare.

While you are in an Advantage plan, a supplement pays nothing. It is one path or the other. See the comparison.

The six month window that decides everything

Your Medigap open enrollment runs six months from the month your Part B starts, at or after 65. During those six months, no company in Texas can decline you or charge you more for your health history.

After that window closes, Texas insurers can ask health questions and say no. The window opens once and does not come back.

Read how the enrollment window works, then see how to enroll when you are ready. If you want us to check where your six months falls, call our McAllen office at (956) 687 3334, or enter your ZIP code in the form on this page.

Common follow-up questions

Is Medigap the same as Medicare Advantage?

No. A supplement pays the share Original Medicare leaves you, while an Advantage plan changes how you receive your Medicare. You can have one or the other, not both.

Does Medigap cover prescriptions?

No. Supplements sold today do not include drug coverage. You add a standalone Part D plan, a drug plan you buy on its own.

Do I need a referral with a supplement?

No. You can go to any doctor who accepts Medicare, with no network and no referral.

Want this looked at properly?

We are an independent agency in McAllen serving Hidalgo, Cameron and Starr counties. There is no obligation to talk it through.

Call (956) 687 3334
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Medicare disclaimer. We do not offer every plan available in your area. Currently we represent 6 organizations which offer 18 products in your area. Please contact Medicare.gov, 1-800-MEDICARE (TTY users call 1-877-486-2048) 24 hours a day / 7 days a week, or your local State Health Insurance Program (SHIP) to get information on all of your options.
Gerino Alejos

Gerino Alejos

Licensed insurance agent · License 3128710 · NPN 18243381

Owner of McAllen Insurance Group, an independent agency on North 10th Street in McAllen. Works with clients across Hidalgo, Cameron and Starr counties on Medicare, Marketplace health, life and auto coverage. Se habla español.