If you have to travel more than 40km to obtain medical services, you can add a per kilometer deduction to your medical expenses. The rate is 52.5 cents per kilometer. You do not have to provide gas receipts, but you should keep any documentation which proves you had the appointment. If you have to travel more than 80 km each way, you can also make a claim for meals and hotels. You need to have receipts for those expenses.
Medical expenses can only be deducted if they exceed 3% of your net income or the $2,397 maximum for 2020. Claiming the mileage will help get the medical expenses to the threshold where you can make a claim. Take a look at your calendar for 2020 and see if you traveled more than 40km one way for medical treatment. If so, you should include the medical mileage on your return.