Buy a vitamin D test and measure your vitamin D level

Vitamin D supports your bone strength, muscle function, and recovery, and also plays a role in your immune system. If you play sport or train intensively, these functions can make the difference between staying fit and repeatedly hitting a wall.

Because your body makes vitamin D mainly from sunlight, a deficiency is common in winter and among people who train mostly indoors. This test gives you a concrete data point: not a diagnosis, but a starting point for a conversation with your doctor.

This test can be of interest if you:

• train seriously and want to optimise your recovery or energy
• train mostly indoors, at a gym or at home
• get little sunlight during the winter months
• notice you catch colds more often or recover more slowly

Even if you are simply curious about your values and want to work on your health with focus, this measurement can give you something to hold on to.

This test measures a single blood value:

• 25-OH vitamin D: the storage form that shows how much vitamin D you have in reserve. To learn more about this value, read our explanation of vitamin D (25-OH).

By measuring 25-OH, you get a reliable view of your stores, as the active form fluctuates more.

Your vitamin D level can show whether your stores are on the low or high side. A vitamin D deficiency is common with little sunlight and can be linked to fatigue, less strength, and slower recovery.

A deficiency is usually recognisable by a low value, while an excess of vitamin D is rare and almost always comes from high doses of supplements. What your value means depends on your situation and is assessed by the doctor.

For this test, blood is drawn at a certified sample point. There are 650+ locations across the Netherlands, so you can often choose one close to home or your gym.

After ordering online, you pick a sample point and a time that suits you. The blood is drawn by trained staff.

You might consider this test when:

• you want to check your values during winter
• you train mostly indoors and get little sun
• you take vitamin D and want to know where you stand
• your recovery or energy lags without a clear reason

Vitamin D changes slowly, so you can have blood drawn at any time of day, which makes planning around your training easy.

Your result shows your value alongside a reference range, so you can see whether it falls within the expected range. What counts as a healthy value varies by lab, season, and person, so numbers alone say little.

A low value can point to a deficiency, while a very high value can, in rare cases, fit with a vitamin D overdose from supplements. That is why a BIG-registered doctor always reviews your result and places it in context.

For a vitamin D measurement you do not need to fast, so you can easily plan the draw around your training or work.

If you take vitamin D in high doses, keep that in mind when reading your result and discuss it with your doctor if needed. Your stores change slowly, so a single day has little effect on the measurement.

Your result is available online within a few working days, with your value, a reference range, and a clear explanation, so you can see where you stand and move forward with focus.

Every blood test result includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP.