Vitamin D in a British winter
Between October and March the sun in the UK is too low for your skin to make meaningful vitamin D, whatever the weather. That is why vitamin D is the marker most likely to be low on a winter report, and one of the few where UK public health advice is clear.
What the NHS advises
The NHS and the UK government advise everyone to consider a daily 10 microgram (400 IU) vitamin D supplement during autumn and winter, and people who get little sun, cover their skin or have darker skin to consider it all year. Higher doses should only be taken on medical advice, because vitamin D builds up and very high intakes over long periods can cause harm.
Why it matters if you train
Vitamin D supports bone, muscle and immune function. Low levels in athletes have been linked with stress fractures and more frequent illness, which is reason enough to know your number before the winter block rather than after it.
Test rather than guess
The test measures 25-hydroxyvitamin D, the storage form, and it is on every Skyline profile from The Health Profile upwards. A result in autumn tells you where you are starting from; a repeat in late winter tells you whether what you are doing is enough. Your GP decides whether a result needs more than the standard supplement.
Getting it in
- Oily fish, eggs and fortified foods help but rarely cover a winter on their own.
- A standard 10 microgram supplement is the baseline the NHS suggests; do not stack products without checking the total.
- Midday daylight on skin from April to September is the main source for most people.
This article is educational. It explains what a marker is and what can move it; it does not interpret your results or replace advice from your GP.
