Area sales manager extending sick leave - Can I ask doctors for advice reports for his reason for this?

Sir my subordinate not performing his duties as expected. When we ask questions he applied for sick leave. He applied for two days he extended 2 More days the two days. He joined 6 months back. He is an area sales manager. His team members are 4. Can I ask doctors for advice reports for his reason for this?
Very urgent reply need. Thanks and regards

Please Ask the records for your verification.
You can also send a warning mail/letter for his performance as per your company norms.
Also Sir, If you have the latest HR Software, You can track his behavior in the HR Portal.

Hi Senthil,
Generally for more than 2 days many companies would ask for a medical report. You can do that. As he had joined 6 months back, you can speak with his supervisor/manager and issue a written warning letter/put him PIP program. Also speak with his reportees and take a feedback on his performance and how good is he as a team player. Beware he might as well look out in this period.

Courts have declared that issuing warning letter to an employee is stigma. As such it should precede legal domestic enquiry.