If you have to get medical attention or treatment during the workday for work related injuries or illness this time spent should be counted as hours worked.
The time spent waiting for and receiving treatment is included in this time. If your employer tells you to go get treatment, the employer can be required to pay for your time because you were injured on the job.
If follow up medical treatments are required during working hours and your employer instructs you to go at that time, then the hours of treatment are considered hours worked. But, if your employer does not instruct you to go, then the hours you are away from work should not be counted as hours worked.