Vitamin D: testing, label amounts and precautions

By DanielUpdated 17 Oct 2026
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30 years in strength training & bodybuilding5 min read
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Vitamin D product labels can use micrograms or IU. This guide explains the quantities, reviews the cited sources and keeps authorised wording separate from individual questions about testing or supplementation.

The authorised claims, verbatim

The box above shows the EU-authorised health claims for vitamin D that are most relevant to people who train, in the exact wording of Commission Regulation (EU) No 432/2012 (consolidated text of 20 August 2025). Each claim stands on its own and its condition of use is shown underneath. We don’t combine, intensify or paraphrase them.

What the studies say, outcome by outcome

Vitamin D status in athletes

A systematic review and meta-analysis pooled 23 studies of 2,313 athletes that measured serum 25-hydroxyvitamin D, the blood marker used to assess vitamin D status (Farrokhyar et al., 2015). Using a cut-off of 32 ng/mL, the authors reported that 56% of the athletes (44–67%) had inadequate levels, and that the proportion varied significantly by geographic location. They also reported a higher risk in winter and spring and in indoor sports, while noting limitations in the evidence and describing the link between vitamin D status and injuries as unclear.

Muscle function: what the trials examined

Two meta-analyses of randomised controlled trials looked at vitamin D supplementation and measures of muscle performance. Beaudart et al. (2014) pooled 30 trials with 5,615 participants (mean age 61.1 years) and assessed muscle strength, muscle mass and muscle power. Han et al. (2024) pooled 10 trials in 354 healthy athletes and assessed handgrip, one-repetition-maximum bench press, vertical jump and quadriceps contraction, using a serum 25-hydroxyvitamin D level above 30 ng/mL as their marker of adequacy. Beaudart et al. conclude that further studies are needed on dose, mode of administration and duration; Han et al. describe the number of available athlete trials as limited. We don’t restate the strength results of either analysis here, because strength is not part of the authorised wording. The only effect on muscle that we state is the authorised claim quoted above.

Testing your level

The two athlete-focused reviews we cite differ on screening. Farrokhyar et al. (2015) call for regular investigation of vitamin D status using reliable assays. Owens et al. (2018) suggest that, in the absence of any pathology, screening may be unnecessary and could result in incorrect supplementation, and argue that the data must be re-examined, taking bioavailable (“free”) vitamin D in ethnically diverse groups into account, so that new thresholds and target concentrations can be established. The same review notes that many athletes now take vitamin D supplements, often at extreme doses, and says it is important to assess whether excessive vitamin D can be detrimental to health.

Amounts, as reported by official sources

These figures come from different bodies for different purposes, so they are not interchangeable.

  • EFSA adequate intake: 15 µg (600 IU) a day for healthy people over one year old, including pregnant and lactating women. EFSA states that its values assume minimal exposure to the sun (EFSA, 2016).
  • EU label reference value: under Article 32 of Regulation (EU) No 1169/2011, a vitamin or mineral declaration on a food label is also expressed as a percentage of the reference intakes in Annex XIII, which gives 5 µg for vitamin D. That is a labelling figure, not EFSA’s adequate intake, so the microgram amount on the label is the number to read.
  • UK health-service advice: the NHS says 10 µg (400 IU) a day is enough for most people who choose to supplement, advises adults not to take more than 100 µg (4,000 IU) a day, and gives 1 µg as equal to 40 IU. It warns that too much vitamin D over a long period can cause calcium to build up in the body (hypercalcaemia). This is UK advice, quoted here because it states a safety ceiling.
  • Foods: the NHS lists oily fish, red meat, egg yolks, fortified foods and liver as dietary sources.

If you have a health condition, take medication, or are pregnant or breastfeeding, speak to a healthcare professional before taking vitamin D supplements.

What we do not say

  • Anything beyond the authorised wording. Regulation 432/2012 lists seven entries for vitamin D (the five shown above, plus teeth and cell division). None covers athletic performance, strength, hormone levels or protection against infections, so we don’t say any of those things. Where the research literature discusses such outcomes, the sources below are the place to read it.
  • A recommended dose for athletes. The sources above give population figures and a safety ceiling, not an athlete-specific target.

Sources

This page is part of the CapyFuel Evidence Library — see how we summarise the research and pick sources. Related evidence pages: omega-3 and electrolytes and hydration; our magnesium guide covers the mineral that often comes up alongside vitamin D. Looking for prices? Our live price pages track protein, creatine, pre-workout and EAA/BCAA products — vitamin D is not one of the tracked categories. See the Malta and Cyprus Price Index, supplement prices in Malta and supplement prices in Cyprus.

Frequently asked questions

Does vitamin D improve athletic performance or strength?

The exact EU-authorised wording is shown in the box on this page. Athletic performance and strength are not part of that wording. Two meta-analyses of randomised trials have examined muscle-strength measures (Beaudart et al., 2014; Han et al., 2024). Both call for further research, and we do not restate their outcomes here.

How much vitamin D do official sources give figures for?

Official sources give different figures for different purposes. EFSA's adequate intake is 15 µg (600 IU) a day for healthy people over one year old (EFSA, 2016). The reference intake used for vitamin declarations on EU food labels is 5 µg. The NHS says 10 µg (400 IU) a day is enough for most people who choose to supplement, and advises adults not to take more than 100 µg (4,000 IU) a day. The microgram amount on the label is the number to read.

How common is low vitamin D status in athletes?

A 2015 systematic review and meta-analysis pooled 23 studies of 2,313 athletes and reported that 56% (44–67%) had vitamin D inadequacy, defined as serum 25-hydroxyvitamin D below 32 ng/mL, with the proportion varying significantly by geographic location (Farrokhyar et al., 2015).

Should athletes have their vitamin D level tested?

The reviews we cite disagree. Farrokhyar et al. (2015) call for regular investigation of vitamin D status using reliable assays. Owens et al. (2018) suggest that, in the absence of any pathology, screening may be unnecessary and could result in incorrect supplementation. A healthcare professional can advise on your own situation.

Sources & further reading

  1. Farrokhyar et al. 2015 — Prevalence of vitamin D inadequacy in athletes: a systematic-review and meta-analysis (Sports Medicine, PubMed)
  2. Beaudart et al. 2014 — The effects of vitamin D on skeletal muscle strength, muscle mass, and muscle power: a systematic review and meta-analysis of randomized controlled trials (J Clin Endocrinol Metab, PubMed)
  3. Han et al. 2024 — Effects of vitamin D3 supplementation on strength of lower and upper extremities in athletes: an updated systematic review and meta-analysis of randomized controlled trials (Frontiers in Nutrition, PMC)
  4. Owens, Allison & Close 2018 — Vitamin D and the Athlete: Current Perspectives and New Challenges (Sports Medicine, PMC)
  5. EFSA 2016 — Dietary reference values for vitamin D (EFSA Journal 14(10):4547)
  6. NHS — Vitamin D
  7. Regulation (EU) No 1169/2011 — food information to consumers, Art. 32 and Annex XIII (EUR-Lex, consolidated 1 Apr 2025)
  8. Commission Regulation (EU) No 432/2012 — authorised health claims, wording and conditions of use (EUR-Lex, consolidated 20 Aug 2025)
  9. EU Register of authorised nutrition and health claims made on foods