Medicare covers many of the healthcare expenses that seniors face, but it alone doesn't extend to every medical bill that you might have to pay. For additional protection, medicare supplement insurance plans -- commonly called Medigap Plans -- offer additional levels of protection. Here are some of the more notable Medigap Plans and the additional coverages they provide.

Medigap Plan A

All of the Medigap Plans are named with a letter, and the first plan is the Medigap Plan A. This is the most limited of these medicare supplement insurance plans, which also means it has the lowest premiums. The Medigap Plan A covers:

• Medicare Part A coinsurance costs
• Medicare Part A hospital costs
• Medicare Part B coinsurance and copay costs
• 3 pints of blood annually
• Medicare Part A hospice costs

Importantly, Medigap Plan A shouldn't be confused with Medicare Part A. The former is a supplemental insurance plan that's privately purchased, while the latter is one of the two main components of government-provided Medicare.

Medigap Plan B

Medigap plan B includes all of the protections that its more limited counterpart, Medigap Plan A, offers. To this list, though, Medigap Plan B policies add coverage for your Medicare Part A deductible. 

While Medigap Plan A will cover Medicare Part A coinsurance costs, these are costs that you only pay once the Medicare Part A deductible has been met. In order to meet this deductible, you may have to spend a substantial amount out-of-pocket if you have no deductible coverage. Medigap plan B adds that deductible coverage.

Medigap plan B also shouldn't be confused with Medicare Part B, as they're two distinct entities.

Medigap Plan C

Medigap plan C further builds on what Medigap Plan B offers, adding coverage for the Medicare Part B deductible as well as other protections. These other protections are particularly enticing for some seniors, as they add protection against some potential expensive medical expenses.

First, Medigap Plan C includes coverage for skilled nursing facilities. Should you need to move to one of these facilities due to a chronic condition, or for a rehabilitation after surgery or illness, this protection will help defray the cost of your care. Depending o how long you have to stay at a facility, the coverage might save you many thousands of dollars.

Second, Medigap Plan C also includes some coverage for emergency care while traveling internationally. The coverage will pay for 80 percent of your foreign emergency care if you travel and need aid.