A vitamin D test with specific dosing advice, rather than a number and a shrug.
Referred by a GMC-registered GP, results reviewed by the same doctor
Taken at a partner site near you
Results explained in plain English, not just a number
Your NHS records in the room, with your consent
Care led personally by Dr Khan
Attentive, unhurried care that listens properly
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Vitamin D behaves more like a hormone than a vitamin. It regulates calcium absorption, and through that affects bone strength, muscle function and immune response.
Deficiency is genuinely common in the UK, for an unavoidable reason: at this latitude the sun is not strong enough between October and March for your skin to make any vitamin D at all, regardless of how much time you spend outside. Everyone's level falls over winter; the question is how far, and from what starting point.
Serum 25-hydroxyvitamin D — the storage form, and the correct measure of vitamin D status. It reflects both what your skin has made and what you have taken in.
UK thresholds are worth knowing plainly: below 25 nmol/L is deficient, 25–50 is insufficient, and above 50 is generally considered adequate. Deficiency below 25 carries a real risk of bone effects — osteomalacia in adults, rickets in children.
What this test does not measure, and should not: the active form, 1,25-dihydroxyvitamin D. It is sometimes requested by people wanting a more complete picture, but it is misleading in ordinary circumstances — it can read normal or even high in someone who is deficient, because the body compensates. It has specific specialist uses and general screening is not one of them.
A broader vitamins and minerals panel measures vitamin D alongside B12, folate, iron, ferritin, zinc, magnesium and calcium, and is often better value where fatigue is the reason for testing, since those deficiencies cluster.
Included: serum 25-hydroxyvitamin D, the standard measure of vitamin D status.
A broader vitamins and minerals panel is available covering vitamin D alongside B12, folate, iron, zinc, magnesium, calcium and total antioxidant status, which is often better value if fatigue is the reason for testing.
1. Consultation. We establish whether testing is actually the right step. For many people the sensible answer is simply to take a standard supplement over winter rather than pay to measure a level that is predictably low — and we will say so.
2. Referral. To a Randox Health clinic. Where fatigue is the reason, we usually request the wider panel with thyroid function and ferritin, because vitamin D is frequently blamed for symptoms something else is causing.
3. The sample. A single blood draw, no fasting. Tell the GP if you already take a supplement — it changes how the result should be read.
4. Results review. A GP explains what your level means and, where treatment is needed, the loading and maintenance doses. Retesting immediately is not useful — allow at least three months for a level to reflect a change.
No fasting required. If you already take a vitamin D supplement, tell the GP — it affects interpretation.
Measured as serum 25-hydroxyvitamin D, in nmol/L:
The evidence is strongest for bone health and weakest for everything else. Vitamin D deficiency causes real bone disease — rickets in children, osteomalacia in adults — and correcting it matters.
The claims made for vitamin D beyond bone health have consistently failed to hold up in large trials, including for cancer prevention, cardiovascular disease and most immune outcomes. That is worth knowing before anyone sells you a high-dose regimen.
Low vitamin D is also frequently a marker rather than a cause. People who are unwell, indoors, inactive or overweight have lower levels — which is not the same as the low level being what is making them unwell.
In the UK the skin makes essentially no vitamin D between October and March, whatever the weather. A level taken in February is your annual low; one taken in September is your annual high.
The same person can produce results 30 nmol/L apart depending on the month.
If you are well and simply want to be sensible, you do not need a test — you need a supplement.
Everyone in the UK is advised to consider 10 micrograms daily from October to March, and year-round for people with darker skin, limited sun exposure, or who cover up. That advice does not depend on knowing your number, and the supplement costs less than the test.
Symptoms of genuine deficiency — bone pain, muscle weakness, proximal weakness getting out of a chair. Malabsorption conditions. Before treating osteoporosis, where correction is needed first. And where a high-dose loading regimen is being considered, which should not be given blind.
For a well person wanting to do the sensible thing, the supplement costs less than the test.
10 micrograms (400 IU) daily, October to March, costs a few pounds a year from any supermarket. Own-brand is identical to branded. Free vitamin D supplements are available through Healthy Start for eligible pregnant women and young children.
We would rather tell you that than sell you a test you did not need.
Symptoms of genuine deficiency, malabsorption, before osteoporosis treatment, or where a loading dose is being considered. In those situations the number changes what happens.
Often not — and it is worth saying plainly. If you are well and want to be sensible, take 10 micrograms daily from October to March and skip the test. The supplement costs less.
Testing earns its place with symptoms of genuine deficiency, malabsorption, before osteoporosis treatment, or where a high-dose regimen is proposed.
Above 50 nmol/L is generally considered adequate. Below 25 is deficient and warrants treatment; 25 to 50 is insufficient.
Above 125 offers no additional benefit, and higher still can cause harm.
Considerably. In the UK the skin makes essentially no vitamin D between October and March, whatever the weather.
A February result is your annual low and a September one your annual high — the same person can produce results 30 nmol/L apart.
Honestly, usually not on its own. Low vitamin D is very common and is frequently found alongside the real explanation rather than being it.
Iron deficiency, thyroid disease, B12 deficiency and sleep apnoea are commoner causes of persistent fatigue, and correcting a vitamin D of 40 rarely transforms how someone feels.
Yes — and this is one of the few vitamins where that is genuinely true. Vitamin D is fat-soluble and accumulates. Excess raises blood calcium and can damage the kidneys.
High-dose products bought online are the usual route to this, and it is a reason not to self-prescribe large doses.
People with darker skin, anyone who covers up or has little sun exposure, people who are housebound, and those with malabsorption conditions.
Pregnant and breastfeeding women, and children under five, are also advised to supplement — and free supplements are available through Healthy Start for those eligible.
Short, regular exposure of forearms and face between late March and September is what the guidance is built around — not sunbathing, and not burning.
Sunscreen reduces production, but the answer is not to skip it. A supplement is a far better trade than sun damage.
Rarely. Once you are supplementing sensibly, repeat testing adds little.
It is worth rechecking after treating a genuine deficiency, or where malabsorption means supplementation may not be working.
Yes — this is where the evidence is strongest. Deficiency causes rickets in children and osteomalacia in adults, and correcting it before treating osteoporosis matters.
But vitamin D is one input into bone health, not a measure of it. Bone density needs a DEXA scan.
Clinically reviewed by Dr Mohammad Zubair Khan, GMC 7563469
Last reviewed
August 23, 2026
On this page
Ongoing
Time to be seen
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Your NHS record in the room
Written treatment plan
Told when a test isn’t needed
Cost
Same day, usually
20 minutes
Yes, with your consent
Included
Yes, and told why
£40 for 20 minutes
Varies by practice
Typically 10 minutes
Yes, your full record
Not routinely
Usually
Free
Same day
Often 10 to 15 minutes
Usually not
Sometimes charged
Varies by provider
Often a subscription
Same-day access is usually available, from 6am to 10pm, seven days a week. You choose a time that suits you rather than waiting on hold at 8am.
Yes. Care is led personally by Dr Mohammad Khan, so you are not passed between clinicians. Continuity is the point of a small practice: someone who knows your history and is listening attentively rather than working through a checklist.
Yes, with your consent. We can access your Summary Care Record during the consultation, so your current medications, allergies and significant history are in the room. That means fewer questions you have already answered elsewhere, and safer prescribing.
No. We are not here to replace GPs, only to support them. Your NHS practice remains responsible for your ongoing care, and with your consent we write to them after the consultation. We are useful when you need to be seen sooner, or want more time than a standard appointment allows.
Twenty unhurried minutes and a comprehensive assessment. A written treatment plan is included, along with any prescription, sick note or referral letter arising from the consultation, at no extra charge.
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It means the diagnosis can usually be made from your history and photographs, and that treatment can be arranged safely without examining you. Where a condition is not marked treatable online, it is because examination is the diagnosis — listening to a chest, feeling an abdomen, examining an ear or a joint — or because a procedure or device is needed.
Yes, where there is a genuine bacterial infection — cellulitis, impetigo, bacterial urine infections, confirmed strep throat. We will also frequently tell you that you do not need one. Most sore throats, coughs, colds and earaches are viral, and an antibiotic gives you the side effects with none of the benefit.
If your problem turns out to be genuinely outside what we can do remotely, the doctor will tell you straight away, point you to the right service, and refund your fee in full. We would rather do that than fill twenty minutes to justify the charge.
Call 999 or go to A&E — do not book an online appointment and do not wait for a reply to an email. For urgent problems that are not emergencies, NHS 111 is available 24 hours a day, online or by phone, and can direct you to the right service.
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