Medical certificates and AI patient confidentiality: what a sick certificate gives away in ChatGPT or Claude.

A medical certificate looks like the least sensitive document a GP writes: a few lines saying a patient is unfit for work. The request behind it is a different matter. Patients explain why they need the time, employers ask for detail, and staff paste the whole exchange into ChatGPT or Claude to word a certificate that says enough and no more. This page marks a certificate and the request that came with it, and shows how the same certificate is prepared on Ermos inside the practice.

The medical certificate for an employer

Written by the GP after seeing the patient, for the patient to give to an employer, university or other organisation. The request often arrives first by email or through the reception desk.

An invented request and certificate. The email address is a reserved example address and the provider number is masked. Hover or tap any highlighted item for the analysis; the full list is below.

What leaves the practice

1. 1
   The patient’s name and date of birth

   Identifies her and her long relationship with the practice. Personal information, held as health information because it was collected in providing a health service. Privacy Act guide.

2. 2
   The employer and a dispute about sick leave

   Where she works, and a manager’s complaint about her attendance. Detail that could be used against her if it travels.

3. 3
   A miscarriage the patient asked to keep private

   A pregnancy and its loss, with a direct request that the employer is not told. Health information, which is sensitive information under the Privacy Act, and a confidence Good medical practice 4.4 asks the doctor to keep. Patient data guide.

4. 4
   Ongoing symptoms and a mental health concern

   Bleeding, poor sleep and a GP’s plan to watch her mood. Patient data guide.

5. 5
   The examination date

   When she was seen, which is the fact the certificate exists to record.

6. 6
   The certificate wording

   States that she was unfit for work and for how long, without the diagnosis. This is the part written for the employer, and it is all the employer needs.

7. 7
   Contact instructions

   An email address and an instruction about home voicemail, which hints that someone at home is not to know. The practice has to be able to follow it. Privacy Act guide.

8. 8
   The certifying GP

   A register name and a masked provider number, linked here to this patient.

What happens in Frontier Models (ChatGPT, Claude)

• The whole document is transmitted to the provider’s servers. On personal plans the user cannot choose where it is stored or processed, and for the major providers that has generally meant outside Australia, under that country’s legal process. Some business plans offer storage in Australia, but the provider still receives the content.
• On consumer tiers, prompts can be retained and used to train future models.
• The provider’s staff and systems can reach the content under the provider’s own policies.
• Once sent, the practice no longer controls it. Retention and deletion happen on the provider’s terms.

The same document on Ermos

Part of AI data leakage in general practitioner (GP) practices. See how this works in practice: Certificates and reports on Ermos.

Common questions