How to check the health certificate on your iPhone is as follows:

1. Open the "Health" application and select the "Health Data" tab.

2. Click the "Profile" icon in the upper right corner.

3. Scroll to the bottom of the page to find the "Health Records" section.

4. Click the "Add Data" button and select the type of health record you want to add.

5. Click the "Save" button and your health record will be saved to your health certificate.

Please note that the health certificate for iPhone requires a digital signature from your doctor or medical institution to ensure the authenticity and accuracy of your health record. Therefore, before obtaining a health certificate, you need to contact your doctor or medical institution to obtain a digital signature.