Is M13 a billable ICD-10-CM code?

No. M13 is a non-billable header code. Code to a higher level of specificity using one of its child codes.

Where does M13 sit in the tabular list?

Diseases of the musculoskeletal system and connective tissue (M00-M99), in the block Inflammatory polyarthropathies (M05-M14).

What cannot be coded together with M13?

M13 carries an Excludes1 note, which means the conditions it lists can never be coded together with it on the same encounter.

M13

M13 — Other arthritis

Non-billable headerICD-10-CM

M13 is a non-billable header ICD-10-CM code for other arthritis. It cannot be billed on its own: choose one of the more specific child codes below.

Excludes1 — never code together

These conditions cannot occur together. Billing both on the same encounter is a denial.

arthrosis (M15-M19)
osteoarthritis (M15-M19)

Other codes that can never be billed with M13

These codes carry an Excludes1 note pointing at M13. The conflict binds both ways, but ICD-10-CM only writes it down on one side — so you would not find this by reading M13 alone.

M06.4Inflammatory polyarthropathy

Risk adjustment

M13 does not map to an HCC and does not risk-adjust under CMS-HCC V28. That is normal — most ICD-10 codes do not. It still needs to be coded correctly; it just will not move a RAF score.

Code to one of these instead M13

3 child codes. Green means billable.

Questions about M13

Is M13 a billable ICD-10-CM code?: No. M13 is a non-billable header code. Code to a higher level of specificity using one of its child codes.
Where does M13 sit in the tabular list?: Diseases of the musculoskeletal system and connective tissue (M00-M99), in the block Inflammatory polyarthropathies (M05-M14).
What cannot be coded together with M13?: M13 carries an Excludes1 note, which means the conditions it lists can never be coded together with it on the same encounter.