Can you tell me whether my client's data counts as HIPAA protected health information?

We cannot tell you whether something is or is not covered by HIPAA. That decision belongs to the health business.

HIPAA relates to storing protected health information (PHI). Sometimes even contact information can count, because it can reveal what kind of treatment a person is getting. The health business knows whether its data is PHI and should tell you whether it needs HIPAA capabilities.