Vitamin D Deficiency: 7 Hidden Signs You Might Have It
Vitamin D deficiency affects an estimated 1 billion people worldwide. The symptoms are subtle — until they're not.
Vitamin D isn't really a vitamin — it's a hormone your skin synthesises from sunlight. And in the modern world, where most of us spend the day indoors, deficiency is the rule rather than the exception. An estimated one billion people worldwide have insufficient vitamin D levels.
Why vitamin D matters
It's involved in:
- Calcium absorption and bone density
- Immune cell function
- Mood regulation (low levels are linked to depression)
- Insulin sensitivity
- Testosterone synthesis
7 signs you might be deficient
1. Persistent fatigue
Even with enough sleep, you feel drained. Vitamin D plays a role in mitochondrial function — your cells' energy production.
2. Low mood or seasonal blues
Vitamin D regulates serotonin synthesis. Several meta-analyses link deficiency to depression risk.
3. Getting sick frequently
D regulates immune cell activity. Low levels are associated with more frequent respiratory infections.
4. Bone or back pain
Without enough D, your body can't absorb calcium properly. Chronic dull bone or low-back pain can be a sign.
5. Hair thinning
Vitamin D receptors are on hair follicles. Low D is linked to alopecia areata and general hair shedding.
6. Slow wound healing
Cuts taking weeks to heal? D plays a role in skin and tissue repair.
7. Muscle weakness
Especially in proximal muscles (thighs, shoulders). Low D affects muscle fibre function.
How to test and supplement
Get a 25-hydroxyvitamin D blood test. Optimal range is generally 40–60 ng/mL (100–150 nmol/L).
If you're below 30 ng/mL, most clinicians recommend:
- 2,000–5,000 IU of D3 per day
- Take with a fatty meal (it's fat-soluble)
- Pair with K2 (MK-7) to direct calcium to bones, not arteries
- Recheck blood levels in 8–12 weeks
Always test before mega-dosing. Vitamin D toxicity is rare but real — and individual response varies widely.
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