For professional drivers in the UK, your licence is more than a card in your wallet. It is your livelihood. And for anyone driving HGVs, buses, or other Group 2 vehicles, that livelihood depends not only on your driving record, but on your medical status.
The D4 medical is the system used to assess that status. While many drivers see it as routine paperwork, it is one of the most common reasons licences are delayed, restricted, or temporarily lost, often due to misunderstandings rather than serious medical problems.
This guide explains how the D4 medical actually works in practice: what the DVLA is assessing, how doctors complete the form, where drivers most often make mistakes, and how to protect your entitlement during renewal or application periods. Whether you are applying for the first time or approaching a renewal deadline, understanding the D4 properly can save you time, stress, and lost income.
What the D4 Medical Really Is
The D4 medical is not a general health check, and it is not a test of fitness or endurance. Its purpose is far narrower and more important.
It is a risk assessment used by the DVLA to determine whether any medical condition you have could reasonably increase the risk of a serious incident when driving large or passenger-carrying vehicles.
The doctor completing your D4 does not decide whether you “pass” or “fail”. Their role is to record medical facts accurately: eyesight measurements, blood pressure readings, declared conditions, and relevant history. The DVLA then applies Group 2 medical standards to those facts and makes the licensing decision.
This distinction matters. Many drivers assume a failed outcome is final. In reality, most delays or refusals occur because information is missing, inconsistent, or unclear, not because driving is permanently ruled out.
For a more detailed explanation of the assessment process, you can read our guide on what is a D4 medical.
Understanding the D2 and D4 Forms
The D4 medical form rarely appears alone. In most cases, it is submitted alongside a D2 application form, and problems often arise when drivers treat them as separate steps rather than parts of the same application.
The D2 form is your declaration. It covers your personal details, the licence categories you are applying for, and your confirmation that the information you are providing is complete and accurate.
The D4 form is medical evidence. It supports what you have declared on the D2 by documenting your medical status at the time of application.
If the two forms do not align, for example, if a condition is mentioned on one but not clearly addressed on the other, the DVLA will pause the application and request clarification. That pause can last weeks or months.
Submitting both forms together, with consistent information, is one of the simplest ways to avoid unnecessary delays.
Who Needs a D4 Medical
The D4 medical applies to Group 2 drivers, where the risks associated with vehicle size, weight, or passenger numbers are higher.
This includes drivers licensed to operate:
- Heavy goods vehicles (HGV)
- Buses and coaches
- Certain larger vans and minibuses
Each of these falls under specific DVLA Group 2 licence categories, which determine when a D4 medical is required and how often it must be renewed.
See a full breakdown of Group 2 licence categories and what they allow you to drive
Taxi and Private Hire Drivers
Taxi and private hire drivers often assume the D4 is a DVLA requirement in the same way it is for HGV drivers. In reality, licensing responsibility sits with local councils (or TfL in London), not the DVLA.
Most councils have adopted Group 2 medical standards because they provide a clear safety benchmark. However, many councils require their own medical form, even if the examination itself mirrors a D4.
This is a common trap. A standard D4 form may be rejected by a council if it does not use their approved paperwork, even if the medical findings are identical. Always confirm council requirements before booking a medical.
How Age Affects D4 Medical Requirements
One of the most misunderstood aspects of Group 2 licensing is how medical frequency changes over time. Many drivers assume that once they have passed a medical, they are covered unless something changes.
That assumption becomes risky after the age of 45.
- Initial application: A D4 medical is required to obtain your first Group 2 licence.
- Up to age 45: No further medical is usually required once your licence is granted.
- Ages 45 to 65: Group 2 licences must be renewed every five years, with a new D4 medical each time.
- Age 65 and over: Licences must be renewed annually, and a D4 medical is required every year.
Missing a renewal deadline results in automatic loss of entitlement, regardless of medical fitness. Planning ahead is essential.
If you’re unsure when your next assessment is due, see our guide on how often you need a D4 medical.
How Long a D4 Medical Is Valid
Once completed and signed, a D4 medical form is valid for four months. This means your full application must reach the DVLA within that window.
If the form expires before submission, a new medical is required. This is a common and avoidable cost, particularly for drivers who book a medical before receiving renewal paperwork.
Who Can Carry Out a D4 Medical
A persistent misconception is that D4 medicals must be completed by your NHS GP. This is not the case.
Any doctor who is:
- Registered with the General Medical Council (GMC)
- Licensed to practise in the UK
can complete a D4 medical.
We also explain when it is appropriate for your GP to complete the assessment in our guide: Can my GP complete my D4 medical?
GP vs Private Providers
Many drivers now choose private providers because:
- Appointments are easier to book
- Evening and weekend slots are available
- Costs are usually lower than GP surgeries
GPs treat D4 medicals as private, non-NHS work and often charge higher fees due to time constraints. Private clinics specialise in driver medicals and operate more efficiently.
Medical Records and History
A doctor can complete a D4 medical without full GP records. However, if you have complex or long-term conditions such as diabetes, heart disease, or neurological issues, the doctor may request a summary of care to ensure accurate reporting.
Accuracy matters more than speed. Incomplete or uncertain medical information is one of the main causes of DVLA follow-ups.
What to Bring to Your Appointment
To avoid delays or repeat visits, here’s what to bring to your D4 medical appointment.
- A completed or blank D4 form
- Photo ID (licence or passport)
- Glasses or contact lenses used for driving
- A list of current medications
- A medical summary if you have ongoing conditions
Your driver number is required, so your photocard licence should be available.
What Happens During a D4 Medical
A D4 medical typically takes 15–30 minutes and focuses on whether you meet DVLA Group 2 medical standards. It is not a full health check, but a targeted assessment relevant to professional driving.
The appointment is usually divided into two parts: an eyesight assessment and a medical evaluation.
Eyesight Standards
You must meet Group 2 vision requirements, which include:
- Visual acuity of at least 6/7.5 in the better eye and 6/60 in the other eye
- Corrective lenses permitted, up to +8 dioptres
- An adequate visual field without significant defects
Some providers complete eyesight testing in-house, while others may require an optician to complete the vision section separately.
Medical Assessment
The medical assessment focuses on conditions that could affect safe driving.
The doctor will assess:
Blood pressure
Your reading must not be persistently above 180/100. A single high reading does not automatically disqualify you, but uncontrolled hypertension will delay completion.
Heart and cardiovascular history
Including angina, heart attacks, heart surgery, strokes, or other circulatory conditions relevant to driving safety.
Neurological conditions
Such as epilepsy, seizures, blackouts, or unexplained loss of consciousness.
Mental health history
Including conditions that could impair concentration, judgement, or reaction time.
Alcohol or drug misuse history
Any past dependency, treatment, or use of substances such as cannabis must be declared honestly, as this may affect DVLA medical decisions.
Physical examination
A brief physical examination is carried out to confirm there are no obvious physical limitations that could affect your ability to safely operate large or passenger-carrying vehicles.
There is no formal hearing test as part of the D4 medical, and a urine test is not a routine requirement. These are not standard screening tests within the D4 assessment, unless specifically advised by the DVLA in relation to a declared medical condition.
If you’d like a step-by-step walkthrough of the appointment, see our full guide on what a D4 medical involves.
Passing, Failing, and Medical Conditions
The doctor does not decide your licence outcome. They record findings. The DVLA decides whether those findings meet Group 2 standards.
High blood pressure, for example, often delays rather than prevents approval. Once controlled, the medical can usually proceed.
Diabetes, including insulin-treated diabetes, does not automatically disqualify drivers, but stricter monitoring and annual reviews apply.
Sleep apnoea can affect licensing outcomes where symptoms such as excessive daytime sleepiness are present, and approval depends on effective treatment and ongoing compliance with DVLA standards.
Mental health conditions must be declared honestly. Well-managed anxiety or depression rarely prevents licensing, but severe or untreated conditions may trigger specialist reports.
Failing to declare a condition is far more serious than declaring one. Non-disclosure can invalidate insurance and is a criminal offence.
We cover this in more depth in our guide on what can make you fail a D4 medical.
After the Medical: Submitting to the DVLA
Once completed, you must send:
- Your D2 application
- Your completed D4 medical
- Your photocard licence
Always keep copies of everything you submit.
Processing times vary. Straightforward cases may be completed in a few weeks. Applications involving additional medical evidence can take several months.
Driving While Waiting: Section 88 Explained
If your licence expires while the DVLA is processing your application, you may be allowed to continue driving under Section 88 of the Road Traffic Act.
This applies if:
- You applied before your licence expired
- You meet medical standards
- You are not disqualified
- Your doctor has not advised you to stop driving
Many drivers carry proof of application while working during this period.
Common Mistakes That Delay Applications
The most frequent causes of delay include:
- Missing signatures or stamps
- Incorrect eyesight entries
- Undeclared conditions
- Inconsistent information between forms
- Expired D4 forms
If you want to reduce the risk of delays caused by incomplete forms or incorrect medical entries, booking your assessment with a provider who completes D4 medicals regularly can make the process much smoother.
Final Thoughts
The D4 medical is not designed to remove drivers from the road. It exists to ensure that those operating the largest and most complex vehicles do so safely.
Most problems arise not from medical unfitness, but from misunderstandings, missed deadlines, or incomplete information. With proper preparation and accurate documentation, the process is usually straightforward.
Understanding the system rather than fearing it is the key to keeping your licence valid and your career moving.
