Hi Michaljaworski,
To achieve this, you would need to create a checkout UI extension and make use of custom fields, and metafields. Shopify allows developers to create custom fields during checkout that customers can use to provide additional information.
You can learn how to create a Checkout UI extension in our docs and once you’ve created your Checkout UI extension, you’ll need to add custom fields to your checkout form (see docs here). This will allow customers to input the necessary personal information. Also you can use client-side validation to validate fields at checkout and block customer progress if the information they provide does not meet your requirements.
The information collected can then be saved using the Metafields API and retrieved when you need to review the customer info with the medication data.
This would be a general approach you could take - I’d recommend checking out the links above and seeing if it would work for your use-case.