1,25-dihydroxyvitamin D (calcitriol)
This test measures 1,25-dihydroxyvitamin D, the biologically active form of vitamin D. It is used to investigate calcium imbalance, kidney disease and...
Vitamin D
48.00
This test measures your Vitamin D level to assess bone, immune, and metabolic health. Vitamin D deficiency is common and often linked to fatigue and low mood.
Turnaround time
1-2 days
Biomarkers count
1
Same-Day Appointments
UKAS Accredited Labs
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Details about Vitamin D
What is a Vitamin D test?
A Vitamin D test measures the level of 25-hydroxyvitamin D (25-OH D) in your blood, which is the best indicator of your body’s Vitamin D stores.
Vitamin D is essential for calcium absorption, bone strength, immune function, muscle health, and mood regulation. Many people in the UK are deficient due to limited sunlight exposure.
Why do I need a Vitamin D test?
Low Vitamin D is a very common hidden cause of fatigue, muscle aches, low immunity, and low mood.
Reasons for testing include:
• Persistent tiredness
• Bone or back pain
• Muscle weakness or cramps
• Frequent infections
• Low mood or seasonal depression
• Hair thinning
• Autoimmune conditions
• Limited sun exposure
• Darker skin tone (higher risk of deficiency)
Benefits of the test
1. Assesses bone and calcium absorption
2. Supports immune system health
3. Helps explain fatigue and low mood
4. Detects a very common deficiency
5. Supports muscle function
6. Important in autoimmune conditions
7. Guides correct supplementation dose
8. Useful for yearly monitoring
Expanded benefit explanation
Vitamin D plays a role in nearly every system in the body. Identifying deficiency allows proper supplementation and symptom improvement.
Step-by-step — How testing works
We offer two UK-wide testing options:
Clinic testing
• Choose nearest UK clinic
• Blood sample collected
• Laboratory analysis performed
• Results securely returned
Home visit (+£60)
• Phlebotomist visits you
• Blood sample collected safely
• Sample sent to lab
• Results delivered confidentially
Your results explained
Low levels
UK reference: < 50 nmol/L
Linked to fatigue, bone pain, low immunity, and mood changes.
Normal levels
UK optimal range: 50–125 nmol/L
Indicates adequate Vitamin D status.
High levels
125 nmol/L may indicate excessive supplementation.
How It Works
Simple steps to get your results
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Book Online
Choose your test online and book in seconds. Select your preferred clinic location or home visit option.
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Visit or Test at Home
Attend one of our UK or London clinics, arrange a home nurse visit, or use a finger-prick kit where available.
3
Get Your Results
Your sample is analysed by accredited UK laboratories, with secure results delivered directly to you.
Take control of your health with London Blood Tests
WhatsApp UsHow to Prepare for Your Test
Follow these guidelines for accurate results
Sample Timing
Where possible, attend your blood test between 7am and 12pm. Please wait until any short-term illness or infection has fully resolved before testing. Avoid intense exercise for 24–48 hours beforehand, as this can affect certain markers.
Fasting & Hydration
Fasting is not always required, but some tests may recommend it. If fasting is advised, avoid food for 8–12 hours before your appointment and drink water only. Stay well hydrated, as this helps with sample collection and accuracy.
Medications & Supplements
Continue prescribed medications unless advised otherwise by your clinician. Avoid vitamin, mineral, or biotin supplements for at least 24–48 hours before your test, as these can interfere with results. If you are unsure about any medication or supplement, please let us know before your appointment.
Hormones & Menstrual Cycle
For hormone-related tests, timing within your menstrual cycle may be important. If relevant, follow any specific guidance provided on your test page.
If you have any questions or special circumstances, our team is happy to advise before your appointment.
Frequently Asked Questions
It measures 25-hydroxyvitamin D, the best indicator of your total vitamin D status.
No fasting is required.
Yes — a phlebotomist can visit your home or hotel anywhere in the UK to collect your blood sample.
Results are usually ready within 1–2 business days.
Generally no, but inform the clinician. Stopping supplements is not necessary unless medically advised.
Fatigue, low mood, muscle pain, frequent illness, bone aches, and sleep disturbance.
Very common — especially in winter or in individuals with limited sun exposure or darker skin.
Yes. Vitamin D influences testosterone, oestrogen, menstrual cycles, and reproductive health.
A GP may recommend higher-dose supplementation and follow-up testing after 8–12 weeks.
Yes — excessive supplementation can lead to high calcium levels. Testing ensures safe dosing.
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