Medical deduction

1. Sec 80D is not a standard deduction but based on the amount of expenditure incurred.  
2. According to explanation 2B of sec 80D, preventive health check-up can be paid in cash to the extent of Rs. 5,000. So, only if you have actually paid and supporting are available such expenses can be claimed as deductions. Even though for the purpose of filing ITR it does not ask for any supporting, but in my sense, it is needed for claiming deductions. 
3. To answer your question some kind of receipts or supportings are needed for claiming the preventive health check-up expenses of Rs. 5,000 as deductions u/s 80D. 
Please correct me if the above solution has an alternative view.