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25-hydroxyvitamin D (25-OHD)

Vitamins & Minerals

45.00

This test measures 25-hydroxyvitamin D, the best indicator of vitamin D stores. It supports assessment of bone, immune, and metabolic health.

Turnaround time

1-2 days

Biomarkers count

1

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Details about 25-hydroxyvitamin D (25-OHD)

Check your vitamin D levels with accuracy and speed

The 25-Hydroxyvitamin D (25-OHD) test is the most accurate way to measure your body’s vitamin D status. Vitamin D plays a vital role in bone health, immune function, energy levels, and mood regulation. Deficiency is extremely common in the UK due to limited sunlight exposure — especially during the winter months.

At London Blood Tests, we offer fast, private vitamin D testing in our London clinics or from the comfort of your home. All samples are processed by UKAS-accredited laboratories, with results typically available within 24–48 hours.

Why test your vitamin D levels?

Low levels of vitamin D can lead to a range of health concerns, including:

Fatigue and low energy
Weakened immunity or frequent infections
Bone pain or muscle weakness
Low mood or symptoms of depression
Poor calcium absorption or brittle bones (osteopenia/osteoporosis)

Early detection allows for targeted supplementation and lifestyle adjustments to restore optimal levels.

About the 25-Hydroxyvitamin D (25-OHD) test

This test measures the main circulating form of vitamin D in your blood — 25-hydroxyvitamin D — which reflects your total vitamin D from sun exposure, diet, and supplements.
It helps determine:

Whether you have vitamin D deficiency or insufficiency
If your current supplementation is effective
The need for clinical treatment or dosage adjustment

Optimal Vitamin D Levels

Vitamin D Level (nmol/L)	Interpretation
Below 30	Deficient
30–50	Insufficient
50–125	Optimal
Above 150	Excess / Toxic range

Who should consider a vitamin D test?

This test is recommended for:

Individuals with limited sun exposure
Those with fatigue, low mood, or bone pain
Vegans or vegetarians
People with malabsorption issues (IBS, coeliac disease)
Elderly adults or individuals with darker skin tones

Book your private vitamin D test in London

Same-day appointments available
In-clinic and home collection options
UKAS-accredited results within 24–48 hours
Professional interpretation and follow-up guidance available

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.

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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

How 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

The 25-hydroxyvitamin D blood test measures the main circulating form of vitamin D in your blood. It is the most accurate test for assessing vitamin D status.

25-OHD reflects vitamin D obtained from sunlight, food and supplements, making it the best indicator of overall vitamin D levels in the body.

This test is recommended if you have fatigue, bone or muscle pain, frequent infections, low mood, limited sun exposure, or risk factors such as darker skin, obesity, or digestive disorders.

No. Fasting is not required for a vitamin D blood test.

UK reference ranges typically are: • Deficient: <25 nmol/L • Insufficient: 25–49 nmol/L • Adequate: 50–125 nmol/L • High: >125 nmol/L Your results should always be interpreted alongside symptoms and clinical context.

Low vitamin D may be associated with: • Bone or joint pain • Muscle weakness • Fatigue • Low immunity • Low mood or depression • Increased fracture risk

Yes. Excessively high vitamin D levels can lead to calcium imbalance, kidney issues and nausea. This is usually due to excessive supplementation rather than sun exposure.

The test requires a simple blood sample, usually taken from a vein in the arm.

Testing frequency depends on your levels and risk factors. Many people test once or twice per year, especially during winter or while supplementing.

Yes. However, it’s important to inform your clinician if you are taking vitamin D supplements, as this helps with accurate interpretation of results.