I’m retired and receive a w2 for imputed income for a domestic partners health care coverage. Does the amount include the Social Security and Medicare taxes?

It sounds like you are saying that the only thing on the W-2 is the value of the health insurance in Box 1 paid for you as a partner. In that case, this amount would be Box 1 only. The health insurance is not subject to social security and medicare.

If anything reported on the W-2 was subject to Social Security tax it would be in Box 3 and the SS withheld would be in Box 4.  Likewise for Medicare, in Boxes 5 and 6 respectively.

Please comment if this is not what you are asking.