I pay a portion of the cost of employer-sponsored health coverage. it's deducted from my paycheck. W2 shows an amount on 12DD, can I claim the portion I pay on medical expenses? or do I assume that the amount on 12DD included my portion?

[BMcCalpin]

The amount with code "DD" in box 12 on the W-2 is the sum of your employer's contributions to your health insurance as well as your contributions to your health insurance as part of a salary reduction program.

By "salary reduction", we mean that you agree to have this amount removed from your Wages as reported on your W-2.

This is why you can't report your "contributions" to health insurance as medical expenses, because they have already been removed from your income. This makes your contributions "pre-tax".

Only if you paid for health insurance premiums with after-tax dollars would you be able to deduct them on Schedule A..