What is the Vitamin D Profile?

The Vitamin D Profile is a blood test designed to evaluate the body’s Vitamin D status by measuring 25-hydroxyvitamin D (25-OH Vitamin D), Vitamin D2 and Vitamin D3. Vitamin D plays a crucial role in bone health, immune function, hormone balance and metabolic regulation.

Vitamin D is often referred to as the “sunshine vitamin” because the body produces it when skin is exposed to sunlight. However, many people—particularly in the UK—develop deficiency due to limited sunlight exposure, indoor lifestyles and seasonal changes.

This test measures the total circulating form of Vitamin D (25-OH Vitamin D), which is the most accurate indicator of Vitamin D stores in the body. It also distinguishes between Vitamin D2 and Vitamin D3, helping clinicians understand whether Vitamin D levels come from dietary sources, supplementation or natural sunlight production.

Biomarkers Included in the Vitamin D Profile

Vitamin D Markers

• 25-Hydroxyvitamin D (25-OH Vitamin D)

• Vitamin D3 (Cholecalciferol)

• Vitamin D2 (Ergocalciferol)

25-OH Vitamin D is the main circulating form of Vitamin D and the standard marker used to assess overall Vitamin D status.

Vitamin D3 (Cholecalciferol) is produced naturally in the skin when exposed to sunlight and is also found in certain foods and supplements.

Vitamin D2 (Ergocalciferol) typically comes from plant-based sources or fortified foods and supplements.

Measuring these markers helps determine both total Vitamin D status and the source of Vitamin D within the body.

Why do I need a Vitamin D test?

Vitamin D deficiency is extremely common, particularly in northern countries such as the UK where sunlight exposure is limited during large parts of the year. Low Vitamin D levels can affect many physiological processes including bone strength, immune function, muscle performance and mood regulation.

Testing Vitamin D levels helps determine whether levels are sufficient, deficient or excessively elevated due to supplementation.

Low Vitamin D may contribute to a wide range of symptoms and health concerns.

Common symptoms associated with Vitamin D deficiency include:

• Persistent fatigue

• Muscle weakness

• Bone pain or joint discomfort

• Frequent infections

• Low mood or seasonal depression

• Hair thinning

• Poor immune function

• Slow recovery from illness

• Reduced exercise performance

• Increased risk of fractures

Vitamin D testing is also commonly recommended for individuals who:

• Spend limited time outdoors

• Use sunscreen regularly

• Have darker skin pigmentation

• Follow restricted diets

• Are pregnant or breastfeeding

• Are over the age of 50

• Take medications that affect Vitamin D metabolism

Because Vitamin D influences immune health, inflammation, hormone balance and bone metabolism, maintaining optimal levels is essential for long-term health.

Benefits of the Vitamin D Profile

1. Detects Vitamin D deficiency
The test identifies whether Vitamin D levels are insufficient, deficient or optimal.

2. Supports bone health assessment
Vitamin D is essential for calcium absorption and bone mineralisation.

3. Immune system monitoring
Adequate Vitamin D levels help support immune function and infection resistance.

4. Helps guide supplementation
Results help determine whether Vitamin D supplementation is needed and at what dosage.

5. Evaluates sources of Vitamin D
By measuring Vitamin D2 and D3 separately, clinicians can determine whether Vitamin D comes from diet, supplements or sunlight.

6. Supports metabolic health
Vitamin D plays a role in insulin sensitivity, metabolic health and cardiovascular risk.

7. Monitors treatment effectiveness
Individuals taking Vitamin D supplements can use this test to monitor progress.

8. Prevents excessive supplementation
High Vitamin D levels can also be harmful, so testing helps ensure safe dosing.

Step by Step

We offer two convenient ways to take this test anywhere in the UK.

Option 1 – Visit a Clinic

• Choose your nearest UK clinic when booking

• Attend your appointment

• A healthcare professional collects your blood sample

• Samples are sent to the laboratory for analysis

• Results are delivered securely

Option 2 – Home or Hotel Visit

For £60 extra, a trained phlebotomist can visit your location.

• Book online

• A phlebotomist travels to your home, office or hotel

• Your blood sample is collected safely and professionally

• No need to travel

Both services are available UK-wide.

Your Results Explained

Low Levels

Low Vitamin D levels indicate deficiency or insufficiency.

Typical UK reference values:

• Deficiency: below 25 nmol/L

• Insufficiency: 25–50 nmol/L

Low Vitamin D may lead to:

• Reduced calcium absorption

• Weak bones and increased fracture risk

• Muscle weakness

• Increased infection risk

• Fatigue and mood changes

In severe cases, deficiency may contribute to osteomalacia in adults or rickets in children.

Normal Levels

Healthy Vitamin D levels support optimal bone health, immune function and metabolic regulation.

Typical optimal UK ranges:

• 50–125 nmol/L

Within this range, Vitamin D helps maintain:

• Strong bones and teeth

• Healthy immune responses

• Balanced calcium metabolism

• Normal muscle function

Maintaining stable Vitamin D levels is important for long-term health and disease prevention.

High Levels

Excessively high Vitamin D levels may occur due to excessive supplementation.

Typical elevated range:

• Above 125–150 nmol/L

Very high levels may lead to Vitamin D toxicity, which can cause elevated calcium levels in the blood.

Potential symptoms may include:

• Nausea or vomiting

• Increased thirst

• Kidney strain

• Calcium imbalance

Monitoring Vitamin D levels helps ensure that supplementation remains within safe ranges.