Do you have to pay out of pocket for the assessment even if the medication itself is covered?

It depends on the provider type. If you see a provider covered under provincial health insurance (like a family doctor), the assessment itself is typically covered the same as any other visit, separate from whether the medication is covered by your drug plan. If you go through a private or virtual platform, the assessment fee is usually a separate out-of-pocket cost regardless of what your insurance covers for the medication itself. References: https://obesitycanada.ca/healthcare-professionals/adult-clinical-practice-guideline/