Is having a kidney transplant considered disabled?

[Critter-3]

Not in and of itself. 

[Opus 17]

"Disabled" for tax purposes means unable to perform substantial gainful work, due to a condition that is permanent, or will last at least one year, or will lead to death.  Many people who have medical disabilities are not disabled for income tax purposes because they can still perform gainful work. 

[xmasbaby0]

For disabled adults:

There is an extra amount added to your standard deduction if you are legally blind.   Your federal return does not provide any other credits or deductions for saying you are disabled, with one possible exception.  

There is a credit for the Elderly and Disabled which is so small that very few people benefit from it—-it has not been updated/increased by Congress for decades.

ELDERLY OR DISABLED CREDIT https://www.irs.gov/help/ita/do-i-qualify-for-the-credit-for-the-elderly-or-disabled

There are some states that provide various credits to elderly/disabled folks, so watch for that when you prepare your state return.   The states that I know of that have anything for elderly/disabled are AZ, CT, DE, IA, MO, ND, NY, VE.   There may be others.

[Opus 17]

@xmasbaby0 , being disabled can also have some benefits for taxpayers who claim a disabled adult as a dependent, both the definition of a dependent and eligibility for the dependent care credit.

Regardless, a person is only disabled for tax purposes if they are unable to work due to their disability.  If a taxpayer is unable to perform gainful work and checks the disabled box (or checks the box for their disabled dependent), Turbotax will identify any potential tax benefits.