Vitamin D
Your bones rely on vitamin D to absorb calcium and maintain strength, but this essential nutrient also supports your energy levels and immune function. With limited sunlight for much of the year, deficiency is incredibly common. This quick blood test checks whether your levels are where they need to be.
Doctor-led
UKAS labs
Results in 2-3 days
Order your Kit
Get a clear snapshot of your health without the hassle. We’ll send the kit and instructions
How it works
Book a home visit
A health professional takes your sample at home or work
From £65
Book a clinic
Professional blood draw at a nearby partner clinic.
From £40
Free tracked return
Post your kit in any Royal Mail postbox with the pre-paid, tracked label.
Doctor-written report
Every Brooksby Medical result is written and reviewed by a GP. You’ll get plain-English explanations for each marker and clear next steps.
Dr James Coleman, MBChB, MRCGP
Founder & GP, Brooksby Medical
Every report is personally reviewed with clear, actionable advice.
Data secure • UKAS-accredited labs • Doctor-led care
What’s measured in this test
Each biomarker helps reveal insights into your health.
Vitamin D
What is Vitamin D?
Vitamin D is an essential nutrient that functions like a hormone. Its main roles are bone and muscle health (helping absorb calcium) and immune support. The majority is made in your skin when exposed to sunlight.
What does a High Result mean?
A higher than expected level usually indicates excessive supplementation. Very high levels can lead to excess calcium in the blood. This is reversible by stopping supplements.
What does a Low Result mean?
A low Vitamin D level is very common in the UK, especially during winter months or with limited sun exposure. Low levels can contribute to tiredness, aches, and long-term bone weakness. Treatment usually involves supplements.
Frequently asked questions
What does a vitamin D blood test measure?
This test measures the level of 25-hydroxyvitamin D in your blood, which is the main circulating form of vitamin D. It reflects your overall vitamin D status from both sunlight exposure and dietary intake, and is the standard marker used by doctors to assess bone health and immune function.
Who should consider a vitamin D test?
Vitamin D testing is particularly useful for:
People who spend limited time outdoors or live in the UK
Those with darker skin tones
Anyone experiencing fatigue, bone pain, or muscle weakness
People supplementing vitamin D who want to check levels
Those with conditions affecting absorption (e.g. coeliac, Crohn's)
What is a normal vitamin D level in the UK?
In the UK, vitamin D levels are typically reported in nmol/L:
Below 25 nmol/L — deficient
25–50 nmol/L — insufficient
50–75 nmol/L — adequate
75–150 nmol/L — optimal
Your GP report will explain where your result falls and recommend next steps.
Do I need to fast for a vitamin D test?
No fasting is required. You can eat and drink normally before this test. Stay well hydrated for an easier blood draw.
How will I receive my vitamin D results?
Secure online results with a GP-written explanation from Brooksby Medical in 2–3 working days.
Related reading
Articles from our GP that relate to this test - explaining your results, what they mean, and when to take action.
THE BRIEFING
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