Coming back to work after being sick or injured is an important milestone in someone's recovery. It's crucial for employers and employees to work together to make this transition as seamless and safe as possible.
Medically reviewed by Dr Sulaiman Shah , MBChB BMedSci, MRCGP — General Practitioner and founder of The GP Clinic. Last reviewed: 16 September 2026
Quick answer: A medical certificate is a formal written statement from a healthcare professional confirming a patient’s health condition and its effect on their ability to work, study, or carry out specific activities. In UK employment, the most common version is the fit note — and contrary to a common assumption, it does not need to disclose your diagnosis to your employer.
Understanding medical certificates properly matters because they sit at the intersection of your health, your privacy, and your legal rights — get the basics wrong and you can end up sharing more than you need to, or less than an employer is entitled to ask for.
A medical certificate is a written statement from a doctor or authorised healthcare professional confirming that they’ve assessed a patient and setting out how a health condition affects that person’s ability to work, study, travel, or take part in a specific activity. It’s used across several settings — the workplace, education, insurance claims, and occasionally court proceedings.
In UK employment specifically, the standard version is the fit note (formally the Statement of Fitness for Work). But “medical certificate” is a broader term — it can also mean a private doctor’s letter confirming a specific fact, a fitness-to-fly letter, or a court-requested medical report, each with a different format and purpose.
This is where a lot of confusion happens, so it’s worth being precise:
| Field | Included? | Notes |
|---|---|---|
| Patient’s name and date of birth | Yes | Standard identifying information |
| Date of assessment | Yes | Confirms when the clinician actually saw/assessed the patient |
| Clinician’s name and registration | Yes | GMC number for doctors, or equivalent professional registration |
| Detailed diagnosis | No, not required | A fit note focuses on functional capability, not the underlying condition |
| General statement of fitness | Yes | “Not fit for work” or “may be fit for work” with any adjustments |
| Recommended duration | Yes | The period the certificate covers |
| Treatment specifics (medication, therapy) | No | Not a standard field on a UK fit note |
Your employer is only entitled to know that you were assessed and are (or aren’t) fit for work, and for how long — not your specific diagnosis, your treatment plan, or your full medical history. A clinician will only include more detail than this if it’s clinically relevant and the patient understands and agrees to it being shared.
People often use these terms interchangeably, but they’re not always the same document:
| Fit Note (Med3) | Private Medical Certificate | |
|---|---|---|
| Who issues it | GP, hospital doctor, or (since 2022) nurse, pharmacist, OT, or physiotherapist | Any appropriately registered private clinician |
| Standard format | Yes — a fixed NHS format | No — tailored to the specific request |
| Typical use | UK employment sickness absence | Insurance, travel, court, specific one-off requests |
| Diagnosis disclosed | No, by default | Only what’s proportionate to the request, with patient understanding |
| Cost | Free via NHS | Usually a private consultation fee |
Medical certificates aren’t just paperwork — used properly, they support the recovery process itself:
For UK fit notes specifically, the list of who can issue one widened in July 2022. Previously, only GPs and hospital doctors could sign you off. Now, the following can also issue a fit note as part of your care:
For private medical certificates — letters for insurance, travel, or specific administrative purposes — the requirement is simply that the clinician is appropriately registered (GMC for doctors, or the relevant professional body for other clinicians) and has genuinely assessed you for the purpose the certificate covers.
The process is broadly the same whether you’re seeing your GP in person or using a private online service:
If you’re specifically after a standard sick note, book an assessment with your GP or an authorised clinician to get one issued.
A medical certificate is your evidence, not your employer’s window into your full medical history. UK rules are deliberately designed to give employers, universities, and insurers what they legitimately need — confirmation that you were assessed and how it affects you — while keeping the underlying diagnosis and treatment private unless you choose to share more. Knowing that distinction protects both your privacy and your ability to get properly documented, so you’re not caught out by requests that go further than what’s actually required.
No. A standard UK fit note focuses on functional fitness for work, not the underlying diagnosis, unless you specifically consent to more detail being shared.
Only with your explicit written consent. Employers can request clarification from the issuing clinician, but the clinician won’t disclose anything beyond the certificate itself without your permission.
Yes, provided it’s issued by an appropriately registered clinician following a genuine assessment. The format may differ, but the legal standing is equivalent for most purposes.
It varies by condition and purpose — from a few days for a minor illness to several months for an ongoing condition. See our detailed guide on how long a sick note can last for the specifics.
Yes. “Medical certificate” covers a range of documents beyond employment sick notes, including academic extenuating circumstances letters, fitness-to-fly letters, and court-requested medical reports — each has its own expected format and level of detail.
Go back to the issuing clinician as soon as you spot it. A corrected version should be issued rather than you altering it yourself — an altered certificate can be treated as invalid or even fraudulent by an employer or organisation relying on it.
Not meaningfully. A clinician can only certify from the point they’ve actually assessed you, whether in person, by phone, or via video. Any period before that assessment is typically covered by self-certification rather than a backdated certificate.
Usually yes, once a previous certificate has expired. Ongoing conditions are typically managed through follow-up assessments and renewed certificates rather than one document covering an indefinite period, so your clinician can confirm your condition is still accurately reflected.
