CNC Medical and
Eyesight Standards
Every Civil Nuclear Constabulary recruit is an Authorised Firearms Officer, so every recruit takes an AFO medical. It rules people out late in the process on points they could have checked on day one: glasses, visual fields, hearing aids and BMI. This guide sets out every standard in the CNC's version 8 guidance, read on 23 October 2026, with a free self-check.
Independent information, not advice · Sources checked 23 October 2026 · England and Wales unless stated
The CNC uses bespoke AFO medical standards. Glasses cannot be used to meet the eyesight standard; contact lenses can. Corrected vision must be 6/12 in either eye and 6/6 with both, with 6/9 near vision, a low contrast test and unaided vision of 6/36 (waived where soft lenses give successful correction). Visual fields must reach 160 by 100 degrees. Hearing aids are not compatible with the role. BMI should be 18.5 to 30, with body fat limits above 30. Medication-controlled diabetes is normally not compatible. Referred cases go to a Pre-Placement Panel. An invitation to assessment does not mean you are medically suitable.
The CNC medical in short
- Glasses: not acceptable for meeting the eyesight standard. Contact lenses can be used.
- Visual fields: 160 by 100 degrees, wider than the 120 by 100 used for Home Office and Police Scotland entry.
- Hearing: no hearing aids, including implanted devices.
- BMI: 18.5 to 30. Above 30, body fat no more than 25% (men) or 32% (women).
- Diabetes: needing medication to control it is normally not compatible.
- Who decides: Occupational Health, with a Pre-Placement Panel for referred cases.
- Timing: the medical runs alongside the rest of recruitment and includes the 7.6 fitness test.
Jump to the free self-check to see which rules apply to you.
Why the CNC standard is stricter than a Home Office force
The CNC says its officers need to meet different medical and fitness standards from Home Office and Police Scotland officers because every officer is an Authorised Firearms Officer who carries "relatively heavy personal protective equipment and kit" and works on licensed nuclear sites.
Its medical guidance says the standards are bespoke and draw on three sources:
- Home Office circular 59/2004;
- College of Policing medical guidance for AFOs, which the CNC describes as "largely aligned to DVLA group 2 guidance"; and
- the ionising radiation regulations.
The guidance tells applicants to refer to the DVLA guidance first. In practice that means the CNC medical has more in common with a professional driving medical than with an ordinary police entry medical.
Version 8 of the guidance (PDF modified 9 October 2025) is linked from the CNC's police officers page. The application process page still links version 7 (January 2024). We use version 8 throughout. A 2022 FOI quoted a BMI range of 19 to 30 from an older version; version 8 says 18.5 to 30.
How the CNC medical works
The medical is a process, not a single appointment. The CNC describes these steps:
- A PNC check first. The medical starts after you pass a Police National Computer check.
- Forms. Occupational Health sends you forms. You need a signed medical declaration from your GP and a signed opticians form.
- Triage. Occupational Health reviews your forms. There are three outcomes: you proceed to the medical and fitness test, the CNC asks your GP or a specialist for more information, or your case is referred to the Pre-Placement Panel.
- The Pre-Placement Panel. It meets about every two weeks. The guidance says it can take up to four weeks before your case is presented.
- The examination, including the fitness assessment.
The guidance says "any invite to assessment centre does not imply medical suitability". You can pass the National Sift, the Online Assessment Centre and the Recruitment Day and still not meet the medical standard. Check the standards before you invest months in the process.
The CNC says the medical "may be held at any point during your recruitment process". It runs alongside the other stages rather than waiting for them to finish.
What the examination covers
| Area | What happens |
|---|---|
| Length and who | Up to 1.5 hours with an Occupational Health physician. You strip to your underwear; a chaperone is available. |
| Ears | Otoscopy and "Audiometry using Bekesy method". |
| Heart | Heart rate, rhythm and blood pressure. |
| Lungs | Lung function by spirometry. |
| Abdomen and urine | Abdominal examination; urine tested for glucose. |
| Skin, joints and spine | Examined. |
| Nervous system | A full neurological examination. |
| Mental health | Your mental health history. |
| Body measurements | Height, weight and BMI. |
| Eyes | Visual acuity and colour vision, plus fundi and visual fields from the optometrist's report. |
| Fitness | The medical includes a fitness assessment: the multi-stage fitness test to level 7.6 (CNC application process and police officers pages). |
The fitness test is the multi-stage fitness test to level 7.6, against 5.4 for most constable recruitment. Our CNC 7.6 bleep test guide has a progression plan from 5.4 to 7.6.
Eyesight standards
| Test | CNC standard |
|---|---|
| Distance, each eye (corrected) | 6/12 in either eye |
| Distance, both eyes (corrected) | 6/6 or better |
| Low contrast distance, both eyes (corrected) | 6/12 or better for a 10% contrast target |
| Near static acuity, both eyes (corrected) | 6/9 or better |
| Unaided, both eyes | 6/36. This need not apply where soft contact lenses give successful correction |
| How you may correct | Contact lenses. "GLASSES ARE NOT ACCEPTABLE to meet the eyesight standard" |
| Visual fields | At least 160 degrees horizontally and 100 degrees vertically, free from large defects (optometrist to confirm) |
| Colour vision | 38-plate Ishihara; if it shows abnormalities, the City University Test (3rd edition) and the Farnsworth-Munsell D15 (see below) |
Your optician records acuity as a fraction such as 6/6 or 6/12. Ask for your readings in that form for each eye and for both eyes together, with and without correction, so you can compare them with the table.
Note that the binocular corrected distance standard (6/6) is stricter than the single-eye one (6/12). A low contrast test is also part of the standard. Ask your optician whether they can test low contrast acuity as well.
Glasses and contact lenses: what the rule means for you
The guidance puts it in capitals: "GLASSES ARE NOT ACCEPTABLE to meet the eyesight standard". This is the rule most likely to surprise applicants who have passed eyesight checks for other forces. Two separate points are easy to mix up:
- Correction: if you need correction to meet the standards, contact lenses can do it; glasses cannot.
- The unaided rule: you need 6/36 with both eyes without any correction, but this "need not apply" where soft contact lenses give successful correction. That is the only thing the soft lens point changes.
How it plays out in common situations (our reading of the guidance; Occupational Health decides):
| Your situation | What it means |
|---|---|
| You wear glasses for distance and your vision without them is good | Your uncorrected vision has to meet the corrected standards on its own (6/12 each eye, 6/6 both eyes, the low contrast and near rules) because glasses cannot be used. Ask your optician for your unaided readings. |
| You wear glasses all the time and have never tried contact lenses | You would need contact lenses that bring you up to the standard. You also need to meet unaided 6/36 with both eyes, unless soft contact lenses give successful correction. Try lenses well before your medical. |
| You wear soft contact lenses and your unaided vision is worse than 6/36 | The guidance says the unaided 6/36 standard need not apply where soft contact lenses give successful correction. You are then judged on your corrected vision with the lenses in. |
| You wear rigid (hard) lenses and your unaided vision is worse than 6/36 | The waiver in the guidance names soft contact lenses. It does not say whether rigid lenses are treated the same way. Ask Occupational Health before you apply. |
| You wear glasses only for reading | Near vision must be 6/9 or better with both eyes, corrected. Glasses cannot be used to meet the standard, so ask Occupational Health how this applies to you before your medical. |
Visual fields: 160 by 100 degrees
The CNC asks the optometrist to confirm a visual field of "at least 160 degrees horizontally and 100 degrees vertically", free from large defects. Home Office and Police Scotland entry uses 120 by 100 degrees, so the CNC asks for 40 degrees more across.
The field result comes from the optometrist's report, not the Occupational Health examination. If your optician does not usually test fields, ask whether they can, or where you could have it done, before your forms arrive.
Colour vision
The CNC uses a three-step path:
- The 38-plate Ishihara test. If it shows no abnormalities, that is the end of colour testing.
- The City University Test (3rd edition) if Ishihara shows abnormalities: you need "less than 3 total errors on part 2".
- The Farnsworth-Munsell D15: you need "less than 2 major crossings".
The guidance lists both further tests for anyone with Ishihara abnormalities. If you know you have a colour vision deficiency, ask your optician whether they can run the City University and D15 tests, or ask Occupational Health how they are arranged.
Laser and other eye surgery
- Corneal weakening: you are "unlikely to be suitable where there is significant weakening of the cornea".
- Waiting time: without that weakening, 6 weeks must have passed since surgery.
- Listed as likely to affect suitability: detached retina, glaucoma and photorefractive keratotomy.
So "six weeks" is not the whole rule. If you are considering surgery to get round the glasses rule, ask the surgeon in writing whether your procedure weakens the cornea and plan at least six weeks before your medical. This is our advice; the guidance does not list which modern procedures it treats as weakening.
Hearing
| Point | CNC standard |
|---|---|
| Hearing aids | Hearing aids, including implanted devices, are "not compatible with the role of AFO" |
| Average loss | Unlikely to be suitable with more than an average of 20 dB loss over 500 to 4,000 Hz |
| Lower frequencies | Unlikely to be suitable with a sum of loss above 84 dB over 0.5, 1 and 2 kHz |
| Higher frequencies | Unlikely to be suitable with a sum of loss above 123 dB over 3, 4 and 6 kHz |
| Ear drum | An active or chronic perforation is unlikely to be suitable |
| How it is tested | Otoscopy and audiometry using the Bekesy method at the medical |
The hearing aid rule is absolute in the guidance: aids are not compatible with the AFO role. If you have noticed any difficulty with hearing, a free hearing test before you apply costs nothing and may save months.
BMI and body fat
- Range: "Healthy BMI should be between 18.5 and 30".
- Above 30: body fat must not exceed 25% for men or 32% for women.
- Outside the limits: employment is deferred until you are within them. The guidance asks you to reach the limit before the medical.
- Evidence: Occupational Health will not sign anyone off as fit without evidence that they meet the BMI or body fat standard.
BMI is weight in kilograms divided by height in metres squared. The table shows the weight range for BMI 18.5 to 30 at common heights:
| Height | Weight at BMI 18.5 | Weight at BMI 30 |
|---|---|---|
| 1.55 m | 44.4 kg | 72.1 kg |
| 1.60 m | 47.4 kg | 76.8 kg |
| 1.65 m | 50.4 kg | 81.7 kg |
| 1.70 m | 53.5 kg | 86.7 kg |
| 1.75 m | 56.7 kg | 91.9 kg |
| 1.80 m | 59.9 kg | 97.2 kg |
| 1.85 m | 63.3 kg | 102.7 kg |
| 1.90 m | 66.8 kg | 108.3 kg |
A man 1.78 m tall who weighs 98 kg has a BMI of 30.9 (98 divided by 1.78 x 1.78). That is above 30, so under the CNC guidance his body fat must be 25% or less. A muscular applicant may meet that; if not, employment is deferred. To be at BMI 30 or below at that height he would need to weigh 95.1 kg or less.
Do not crash diet before the medical. The same appointment includes a shuttle test to level 7.6. Under-fuelling costs levels. A steady loss with regular running helps both.
Blood pressure, diabetes and other conditions
The guidance lists these conditions. How your own case is handled depends on triage: you proceed, the CNC asks your GP or specialist for information or your case goes to the Pre-Placement Panel.
| Area | What the guidance says |
|---|---|
| Blood pressure | Above 140/90: you are referred to your GP. Recruitment continues once your blood pressure is stable with no side effects from any medication. |
| Diabetes | Needing medication to control diabetes is "normally not compatible". Diet-controlled diabetes is risk assessed. |
| Respiratory | Asthma "currently in treatment including inhalers" and exercise-induced asthma are listed, with FEV1 below 75%, FEV1/FVC below 70% or below the predicted norm. |
| Musculoskeletal | Hip or knee replacement, laminectomy, major joint surgery, recurrent dislocation, cervical discectomy and multi-level lumbar disease are listed as likely to affect suitability. |
| Blood and circulation | Anticoagulants including warfarin, sickle cell disease and polycythaemia are listed. |
| Bowel | Unresolved Crohn's disease or ulcerative colitis and a stoma are listed. |
| Skin | Widespread eczema or psoriasis is listed. |
| Communication | Any condition affecting radio communication is listed. |
| Height | No height rule is published. |
If a condition on this list applies to you, gather the letters and test results you already have before your forms arrive. Specialist evidence takes time to obtain.
Mental health
The guidance sets stability periods by severity:
| History | What the guidance says |
|---|---|
| Minor or more severe anxiety or depression, without significant memory, concentration or risk features | Risk assessed by the Pre-Placement Panel. Normally at least 6 months stable and 6 months off treatment. |
| More severe illness, or more than two episodes | At least 12 months stable and 12 months off treatment, plus a specialist opinion. |
| Psychotic disorders | At least three years symptom-free and off medication. |
Those are the normal minimum periods, not automatic decisions. Declare your history fully. A history that is declared and explained is assessed on the evidence; one found later raises an honesty question as well.
Drug testing
The CNC tests applicants for drugs. Its 2021 FOI response says it ran 375 pre-employment substance misuse tests in 2019/20, plus 149 random tests. All five non-negative screens were explained by declared prescription medication or another legitimate source. A 2025 FOI response says no officer tested positive after laboratory analysis and Medical Review Officer review between 2019 and 2025.
The current careers pages do not name a drug test stage or say whether a hair or urine sample is used. Declare all prescription and over-the-counter medication when asked.
Free CNC medical self-check
Answer a few questions to see which CNC medical rules apply to you and what to ask about. The self-check only reflects the published guidance. It cannot clear you: Occupational Health and the Pre-Placement Panel decide.
Free tool
CNC medical self-check
Against the CNC's AFO pre-employment medical guidance (version 8, October 2025). Your answers never leave this page. It is not a medical opinion: the CNC's Occupational Health team and Pre-Placement Panel decide.
CNC vs MOD Police: the two AFO medicals compared
The MOD Police also recruits every constable as an armed officer and applies AFO medical standards to every applicant. The two forces' published standards are close in places and different in others:
| Civil Nuclear Constabulary | MOD Police | |
|---|---|---|
| Correction for eyesight | Glasses are not acceptable; contact lenses can be used | Standards stated as "aided or unaided". Ask the MDP how it treats glasses |
| Distance acuity | Corrected 6/12 in either eye and 6/6 or better with both eyes | Binocular 6/7.5; at least 6/12 in the worse eye |
| Unaided acuity | 6/36 with both eyes, unless soft contact lenses give successful correction | Binocular 6/36 or better, unless corrected with soft contact lenses |
| Near vision | Corrected 6/9 or better with both eyes | N8 corrected and uncorrected |
| Low contrast | Corrected 6/12 or better for a 10% contrast target | No separate standard in the MDP's published list |
| Visual fields | At least 160 by 100 degrees (optometrist) | At least 120 by 100 degrees, by confrontation testing of each eye |
| Colour vision | If Ishihara shows abnormalities: City University (3rd edition) fewer than 3 total errors on part 2 and D15 fewer than 2 major crossings | Dichromats, severe anomalous trichromats and monochromats unsuitable; D15 fails at 2 or more major crossings; City University fails at set error counts; colour-correcting lenses not accepted |
| Eye surgery | 6 weeks if the cornea is not significantly weakened; detached retina, glaucoma and photorefractive keratotomy likely to affect suitability | At least 6 weeks with no residual side effects; LASIK, LASEK, PRK and ICRS can be considered |
| Hearing | No hearing aids; 20 dB average rule; 84 dB and 123 dB sums | Unaided standard; 84 dB and 123 dB sums; annual audiometry for all firearms officers |
| BMI | 18.5 to 30; above 30, body fat no more than 25% (men) or 32% (women) | Below 30 and no lower than 19 with a waist under 40 inches (men) or 35 inches (women); waist to hip ratio or body fat (21% men, 30% women) as alternatives |
| Blood pressure | Above 140/90: GP referral, continue once stable | Consistently 140/90 or more: not suitable for AFO |
| Diabetes | Medication-controlled normally not compatible; diet-controlled risk assessed | Type 1 unlikely to be suitable, case by case |
| Asthma | Listed, including asthma treated with inhalers, with spirometry thresholds | Assessed individually; may be accepted if managed with medication |
| Drug testing | Pre-employment testing exists (FOI); method not published | Drug and alcohol testing at the medical |
| Fitness test | Multi-stage fitness test to level 7.6 | PES-JRFT in a 20 kg vest |
Two differences matter most. The MDP's visual field standard is 120 by 100 degrees against the CNC's 160 by 100. The BMI rules work differently: the CNC allows BMI above 30 with a body fat limit, while the MDP sets a BMI range plus waist measurements, with waist to hip ratio and body fat as alternatives. Full detail is in our MOD Police medical standards guide and the CNC vs MOD Police comparison.
How to prepare for the CNC medical
Our advice, in the order we would do it. Not medical advice: speak to your GP or optician about your own health.
| When | What to do |
|---|---|
| Now | Book an eye test. Ask for your unaided and corrected acuity for each eye and both eyes, your near vision and whether a visual field test is possible. Write the numbers down. |
| Now, if you wear glasses | Ask your optician about contact lenses and start a trial. You want months of comfortable wear behind you, not a first pair the week before your medical. |
| Now, if you are planning eye surgery | Allow at least six weeks before your medical. Ask your surgeon whether the procedure weakens the cornea and get that in writing. |
| Within a month | Have a hearing test if you have any doubt. Check your blood pressure at a pharmacy. Work out your BMI; if it is above 30, find out your body fat percentage. |
| Before the forms arrive | Collect letters about any past condition, operation or treatment. Your GP completes a medical declaration; specialist letters may be requested. |
| Throughout | Answer every medical question fully. Do not stop prescribed medication to pass a medical without medical advice. Email medicals@cnc.police.uk with specific questions. |
Medical queries go to medicals@cnc.police.uk, the contact given in the guidance. Ask specific questions ("I wear rigid lenses and my unaided vision is 6/60: does the soft lens waiver apply?") rather than general ones.
What the CNC does not publish
- Whether rigid contact lenses are treated like soft lenses for the unaided 6/36 rule.
- Which eye surgery procedures it treats as significantly weakening the cornea.
- The drug test sample type (hair or urine) and when in the process the test happens.
- Who carries out the medical or where.
- Whether you pay for the GP declaration or the optician's form.
- The track length, number of attempts or retest rules for the 7.6 fitness assessment.
- How often serving officers are medically reassessed, apart from the annual fitness test.
If your invitation or Occupational Health tells you any of these, that takes priority over this page.
Frequently Asked Questions
Can you wear glasses in the Civil Nuclear Constabulary?
Not to meet the eyesight standard. The CNC's pre-employment medical guidance (version 8) says "GLASSES ARE NOT ACCEPTABLE to meet the eyesight standard". If you need correction, contact lenses are the route. This is a major difference from Home Office forces and Police Scotland.
Can I join the CNC if I wear contact lenses?
Yes, contact lenses can be used to meet the corrected standards. You also need unaided vision of 6/36 with both eyes, but the guidance says that unaided rule need not apply where soft contact lenses give successful correction. It does not say the same about rigid lenses, so ask Occupational Health if you wear those.
What is the CNC eyesight standard?
Corrected distance vision of 6/12 in either eye and 6/6 or better with both eyes; corrected low contrast vision of 6/12 or better for a 10% contrast target; corrected near vision of 6/9 or better; unaided vision of 6/36 with both eyes; visual fields of at least 160 degrees horizontally and 100 degrees vertically; and colour vision checked by Ishihara, with further tests if it shows abnormalities.
Can I join the CNC after laser eye surgery?
Possibly. The guidance says you are unlikely to be suitable where there is significant weakening of the cornea. Without that, 6 weeks must have passed since surgery. Detached retina, glaucoma and photorefractive keratotomy are listed as likely to affect suitability.
What is the CNC BMI limit?
A healthy BMI should be between 18.5 and 30. Above 30, your body fat must not exceed 25% if you are a man or 32% if you are a woman. Employment is deferred until you are within the limits, so reach them before your medical. Occupational Health will not sign you off as fit without evidence that you meet the BMI or body fat standard.
Can I join the CNC with asthma?
The guidance lists asthma currently in treatment including inhalers and exercise-induced asthma, along with spirometry results of FEV1 below 75%, FEV1/FVC below 70% or below the predicted norm. How your case is handled depends on triage: you may proceed, the CNC may ask your GP or specialist for information or you may be referred to the Pre-Placement Panel.
Can I join the CNC with a hearing aid?
No. The guidance says hearing aids, including implanted devices, are not compatible with the role of AFO. Hearing is tested at the medical using the Bekesy audiometry method.
Is there a height requirement for the CNC?
No height rule is published in the CNC's medical guidance or on its police officers page.
Does the CNC drug test applicants?
Yes. A 2021 FOI response says the CNC ran 375 pre-employment substance misuse tests in 2019/20 (plus 149 random tests). The current careers pages do not name the drug test stage or say what kind of sample is taken.
How long does the CNC medical process take?
The examination itself takes up to 1.5 hours. If your forms are referred to the Pre-Placement Panel, which meets about every two weeks, the guidance says it can take up to four weeks before your case is presented. The medical runs alongside the rest of the recruitment process and may be held at any point.
Sources and how we checked them
Every factual claim on this page was written from the sources below, read on 23 October 2026. Rules and figures change, so check the source for the date you are reading this. Where we could not confirm something from an official or independent source, the page says so rather than guessing. Spotted something out of date? See our corrections policy.
- CNC Authorised Firearms Officer Pre-employment Medical Guidance, version 8 (PDF, modified 9 October 2025) : every medical, eyesight, hearing, BMI and condition standard on this page; basis; triage and the Pre-Placement Panel; the examination; medicals contact (accessed 23 October 2026)
- CNC pre-employment medical guidance, version 7 (PDF, January 2024) : older version still linked from the application process page; this page uses v8 (accessed 23 October 2026)
- CNC careers: Police officers : different medical and fitness standards from Home Office and Police Scotland officers; AFO role; heavy personal protective equipment; 7.6 fitness standard (accessed 23 October 2026)
- CNC careers: Applying for a role (application process) : GP declaration, opticians form, medical examination including a fitness assessment at any point; Occupational Health contact after the online stage (accessed 23 October 2026)
- CNC FOI 2022/057: officer recruits and BMI (PDF) : older guidance quoted a BMI range of 19 to 30 (accessed 23 October 2026)
- CNC FOI 057: substance misuse tests 2019/20 (PDF) : 375 pre-employment and 149 random tests; all 5 non-negative screens explained (accessed 23 October 2026)
- CNC FOI 2025/123: drug testing of officers (PDF) : no officer tested positive after laboratory analysis and MRO review, 2019 to 2025 (accessed 23 October 2026)
- MOD Police careers: Medical : MDP AFO medical standards used in the comparison table (accessed 23 October 2026)
- MOD Police careers: Fitness : PES-JRFT in a 20 kg vest (accessed 23 October 2026)
On this topic elsewhere
More in this guide series
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Disclaimer
PolicePay.co.uk is an independent guide. It is not affiliated with the Ministry of Defence Police, the Ministry of Defence, the Civil Nuclear Constabulary, the Civil Nuclear Police Authority, the Defence Police Federation, the Civil Nuclear Police Federation, the College of Policing or any other force. It does not recruit, vet or assess applicants. Every fact here comes from the force's own pages, GOV.UK, legislation.gov.uk or the other sources listed, read on the date shown. Each force sets and changes its own process and pay: check its current pages and your own invitation before relying on anything here. Our practice questions are original PolicePay material, not questions used by either force. Details are as checked on 23 October 2026.