Vitamin D: the only one almost everyone needs
If you could keep only one supplement, this would be it. Vitamin D does not come from food: egg yolk and fatty fish provide tiny amounts; the main source is skin exposed to sunlight. From October to April in our latitudes, the sun does not provide enough ultraviolet radiation; in summer, sunscreen, clothing, and the office get in the way. The result: deficiency in 40% of adults, more often in women over 45. Section — vitamins and minerals.
What it does and what deficiency looks like
Calcium for bones, muscle strength, immunity, and mood. With a deficiency: unexplained fatigue, muscle and bone pain, frequent colds, winter low mood, and in women over 45, accelerated bone loss. Symptoms are vague and attributed to “age” and “stress,” so without testing, deficiency can persist for years. About bones after 45 — bones and muscles after 45.
30-50
ng/mL — target level
1000-2000
IU D3 per day
3 months
before retesting
with fat
the only way to absorb it
Level — what to do
| 25(OH)D, ng/mL | Assessment | Action |
|---|---|---|
| below 10 | severe deficiency | doctor, therapeutic dose, monitoring |
| 10-20 | deficiency | 2000-4000 IU as prescribed, retest after 3 months |
| 20-30 | insufficiency | 2000 IU daily, retest after 3 months |
| 30-50 | normal range | 1000-2000 IU from October to April |
| 50-80 | high-normal range | maintenance 1000 IU or a summer break |
| above 100 | excess | stop taking it, monitor calcium |
How to take it
D3 (cholecalciferol), not D2. Take it with food containing fat — eggs, avocado, fish, oil: without fat, absorption is twice as poor. Daily rather than a large weekly dose — more evenly. In the morning or during the day: for some people, taking it in the evening interferes with sleep. With doses above 2000 IU, it is reasonable to add K2 100-200 µg — it directs calcium to the bones rather than the blood vessels. Magnesium is needed to convert D into its active form — another reason to keep it within the normal range: magnesium.
When too much is also bad
Vitamin D is fat-soluble and accumulates. Taking 5000-10000 IU every day for years without testing is a path to excess calcium in the blood: nausea, weakness, and kidney stones. So there is one rule — dose according to the test, retest after three months, and take a break in summer when there is sufficient sunlight. A multivitamin with 400 IU does not solve the problem; 10000 IU “for prevention” creates one.
Frequently asked questions
Can I stop taking it in summer?
If you spend 15-20 minutes in the sun with your arms and legs uncovered and no sunscreen — yes. Office, sunscreen, clothing — take it year-round. A test in September will show.
Drops or capsules?
It makes no difference if it is D3 taken with fatty food. Oil drops are absorbed slightly better.
Are vitamin D deficiency and excess weight connected?
Yes, in both directions: fat “hides” vitamin D, while deficiency worsens insulin sensitivity. When weight decreases, the level often rises on its own.
- What You Need and What You Don’t
- Vitamins and Minerals
- Electrolytes and Hydration
Reviewed by Anastasia Zhukova, Fitness Trainer • Author of a Nutrition and Training System • Creator of an AI Personal Support Platform
A human has reviewed this material against the method and real client practice.