5 AIs asked about Vitamin D half-life (using VitaminDWiki)

Claude AI Feb 2025

Here's what VitaminDWiki says about how long vitamin D stays in your system, Henry:

  • The overall half-life of vitamin D in the body ranges from roughly 1 to 6 weeks, depending on the form, source, and the person's current blood level. At that point, half of the circulating amount has been metabolized or cleared.

  • Vitamin D from sun/UV exposure has the longest half-life — approximately 6 weeks at a blood level around 20 ng/mL. This is because UV-produced D3 is stored efficiently in fat and released gradually.

  • Vitamin D3 from oral supplements has a half-life of about 3 weeks (again at ~20 ng/mL), while vitamin D2 supplements have a much shorter half-life of roughly 1 week, making D3 far more persistent in the body.

  • Half-life is inversely related to blood level. At low levels (~10 ng/mL), the half-life of sun-derived vitamin D is about 12 weeks. At high levels (~50 ng/mL), it shrinks to about 2 weeks. At very high levels, the half-life may be measured in just days.

  • A specific study using stable-isotope tracers found that 25(OH)D3 has a mean half-life of ~15 days, while 25(OH)D2 has a mean half-life of ~14 days (Jones et al., 2014). The D2 half-life was significantly shorter, especially in Gambian men (~12.8 vs. 14.7 days).

  • The total-body half-life of vitamin D3 (parent compound) is approximately 2 months when its storage in adipose (fat) tissue is accounted for. In the blood alone, the serum half-life of D3 itself is much shorter — only 36 to 78 hours after UV exposure.

  • The active hormone calcitriol (1,25(OH)₂D) has a very short half-life of only 3.5 to 21 hours, which is why the body tightly regulates its production on demand from the 25(OH)D pool. The pharmacologic activity of an administered dose of calcitriol lasts about 3 to 5 days.

  • After a single dose of 100,000 IU starting at 27 ng/mL, the half-life was observed to be approximately 50 days (~7 weeks), consistent with VitaminDWiki's summary that the circulating metabolite 25(OH)D has a serum half-life of 4–6 weeks.

  • It takes 4 to 5 times the half-life to reach a steady state, meaning if your half-life is 2–6 weeks, it will take approximately 2–6 months of consistent dosing before blood levels stabilize at a new plateau.

  • Half-life is also affected by vitamin D–binding protein (DBP) concentration and genetics. Higher DBP levels are associated with longer half-lives, and certain DBP genotypes (e.g., Gc1f/1f homozygotes) are associated with shorter half-lives.

  • Trauma and surgery can cause vitamin D levels to crash dramatically — the half-life in acute illness/trauma may be as short as 1–2 days. Fat-soluble vitamins including D can decrease by ~59% within a single day after major trauma.

  • Inflammation and sickness may shorten the effective half-life to roughly 2 days, as the body rapidly consumes vitamin D during immune activation.

  • Vitamin D is fat-soluble and stored in adipose tissue, which acts as a reservoir for time-release. Dr. Robert Heaney found that at an intake of 2,200 IU/day, the body only stores about a 12-day supply — meaning fat reserves are "essentially running on empty" at typical intake levels.

  • Other factors that may modify how long vitamin D stays in the system include obesity (more fat tissue sequesters more D, paradoxically lowering blood levels), race, type of food consumed, and the ratio of UVB to UVA exposure (excess UVA can degrade vitamin D).

VitaminDWiki references

  1. https://vitamindwiki.com/Half-life+of+vitamin+D+varies
  2. https://vitamindwiki.com/Take+vitamin+D3+daily,+weekly,+or+bi-weekly
  3. https://vitamindwiki.com/Factors+including+skin+temperature)+Influencing+Vitamin+D+Status+%E2%80%93+2011
  4. https://vitamindwiki.com/Should+You+Worry+if+You+Store+Vitamin+D+in+your+body
  5. https://vitamindwiki.com/Overview+Loading+of+vitamin+D
  6. https://vitamindwiki.com/Overview+Toxicity+of+vitamin+D
  7. https://vitamindwiki.com/pages/30-to-50-ng-of-vitamin-d-is-optimal-central-europe-consensus/
  8. https://vitamindwiki.com/pages/vitamin-d-frequently-asked-questions-2011/
  9. https://vitamindwiki.com/Vitamin+D3+becomes+Calcidiol+which+becomes+Calcitriol

Chat GPT (5 minutes of deep research)

Vitamin D3 Retention After Stopping Supplementation Half-life varies by level/source: 25(OH)D’s decay rate depends on starting level and source[1][2]. For example, at ∼20 ng/mL (with sun/UV source) the 25(OH)D half-life is estimated ≈6 weeks[1], whereas at ∼50 ng/mL it drops to only ≈2 weeks[2]. (With D3 supplements, half-life is ≈3 weeks; with D2 ≈1 week[1].)

Longer half-life at low levels: When blood 25(OH)D is low (≈10–20 ng/mL), it clears very slowly – on the order of several months. In one model, sun-derived 25(OH)D at ∼10 ng/mL had a half-life ≈12 weeks, vs ≈2 weeks at 50 ng/mL[2]. In practice, experts estimate a ∼6-week half-life around 20 ng/mL[1], but much shorter at high levels.

Circulating 25(OH)D is long-lived: The main blood form 25(OH)D has a long residence time (much longer than typical steroids). Reports cite a circulating half-life of ~15–60 days (and even up to ~120 days)[3], reflecting slow clearance via storage/release mechanisms.

D3 vs D2 clearance: Vitamin D3 persists far longer in the body than vitamin D2. Clinically, D2 “stays in the body for a much shorter period” – requiring daily dosing – whereas D3 can be dosed every 2 weeks or even monthly[4]. This reflects better storage of D3.

Rapid decline when very high: After extreme overdoses, 25(OH)D levels fall over months. In case reports, super-high levels (>600 ng/mL) fell back to normal within a few months after stopping[5], but at typical levels (20–50 ng/mL) the decay is more gradual.

Clinical guidance (half-life ~15 d): Because 25(OH)D₃’s half-life is ~15 days[6], physicians recommend stopping vitamin D supplements ~20–30 days before a blood test[6]. This implies roughly 1–2 half-lives (50–75% reduction) between dosing and testing.

Serum 25(OH)D half-life ~3 weeks: Overall, 25(OH)D is said to persist ~3 weeks on average[7] (compared to only 5–8 h for active 1,25(OH)₂D[7]). Thus after stopping D3, levels decline by about half every 2–4 weeks, depending on starting level. Fat and tissue stores slow decline: Vitamin D accumulates in fat and other tissues, slowing its fall. In a long-term study (20,000 IU/week for 3–5 years), subjects’ 25(OH)D fell only from ~49→34 ng/mL over 12 months off treatment[8][9]. By contrast, controls were ~28→29 ng/mL. This shows high stored levels bleed off slowly. Adipose D reserves: In that study, fat-tissue vitamin D dropped ~52% in one year after stopping[10]. The persistent adipose vitamin D likely released over time to keep serum 25(OH)D higher for months.

Dose-dependent decline: Supplement dose and peak level affect decline. In one trial, 2,000 IU/day raised 25(OH)D modestly and levels stayed stable after a break, whereas 4,000–8,000 IU/day (raising 25(OH)D to ~40–60 ng/mL) produced much larger drops when stopped[11]. In other words, larger spikes (50+ ng/mL) fall more sharply.

Possible muscle reservoir: Since blood 25(OH)D lasts so long, researchers hypothesize an extravascular “storage.” For instance, 25(OH)D may shuttle into/out of muscle tissue[12]. Supporting this, experiments show radiolabeled vitamin D in pregnant rats largely appeared as 25(OH)D in pups’ muscle[13].

Practical retention: In summary, after stopping D3 supplements, 25(OH)D levels usually decline over weeks–months. Lower starting levels (~20 ng/mL) correspond to slower decay (half-life on order of 1–2 months) while very high levels (50+ ng/mL) clear more rapidly (half-life on order of weeks)[1][2].

Sources: VitaminDWiki pages on vitamin D half-life and storage

(as cited above)[1][2][6][3][12][13][4][7][8][9][10][11]. Each bullet is based on data or estimates from these sources.

[1]

[2] Half-life of vitamin D varies - VitaminDWiki https://vitamindwiki.com/pages/half-life-of-vitamin-d-varies/

[3] [12] [13] Vitamin D stored in muscle via Vitamin D Binding Protein - VitaminDWiki https://vitamindwiki.com/pages/vitamin-d-stored-in-muscle-via-vitamin-d-binding-protein/

[4] VitaminDWiki interview and transcript - Lahore - VitaminDWiki https://vitamindwiki.com/pages/vitamindwiki-interview-and-transcript-lahore/

[5] 10,000 IU of Vitamin D for 7 years with no excessive Calcium in 4,800 patients - VitaminDWiki https://vitamindwiki.com/pages/10000-iu-of-vitamin-d-for-7-years-with-no-excessive-calcium-in-4800-patients/

[6] Vitamin D and RCTs (Randomized Controlled Trials) - VitaminDWiki https://vitamindwiki.com/pages/vitamin-d-and-rcts-randomized-controlled-trials/

[7] Loading dose of 300,000 IU Vitamin D got most above 20 ng in a week - VitaminDWiki https://vitamindwiki.com/pages/loading-dose-of-300000-iu-vitamin-d-got-most-above-20-ng-in-a-week/

[8] [9] [10] Vitamin D stored in fatty tissue may have half life of 12 months (vs 2 months otherwise) - VitaminDWiki https://vitamindwiki.com/pages/vitamin-d-stored-in-fatty-tissue-may-have-half-life-of-12-months-vs-2-months-otherwise/

[11] 40 ng response to 4,000 IU daily Vitamin D for 2 months (and 60 ng for 8,000 IU) - VitaminDWiki https://vitamindwiki.com/pages/40-ng-response-to-4000-iu-daily-vitamin-d-for-2-months-and-60-ng-for-8000-iu/

Deep Seek Feb 2026 - less than 1 minute, links are online

Based only on the information available on VitaminDWiki.com, here are 10-15 bullet answers regarding how long vitamin D stays in your system. The exact URLs are provided for each citation.

  • Unprocessed vitamin D (cholecalciferol) has a very short half-life of approximately one day in the serum .
  • The main circulating form, 25-hydroxyvitamin D (25(OH)D), has a half-life of approximately 3 weeks in the circulation .
  • This 3-week half-life varies depending on initial levels: the lower the initial vitamin D level, the longer the half-life .
  • 25-hydroxyvitamin D2 (the active form of D2) has a terminal half-life of approximately 13.4 days in plasma .
  • When stored in adipose (fatty) tissue, vitamin D has a half-life of approximately 12 months. A specific study showed that adipose tissue vitamin D levels decreased by 52% over 12 months .
  • This storage in fat acts as a "time-release" mechanism, allowing the body to access vitamin D during seasons or periods without sun .
  • Dr. Robert Heaney found that if you take 2,200 IU per day, you only have about 12 days supply of vitamin D in your body, indicating that most people are "running on empty" regarding fat reserves .
  • It can take 3 to 12 months for vitamin D levels to come to a new plateau after changing supplementation habits .
  • Even after 12 months of supplementation, levels may not have plateaued. One study administering 50,000 IU monthly noted that vitamin D levels were still rising at the 12-month mark .
  • Vitamin D stored in fat tissue during a 5-year intervention has a clinically relevant effect on serum levels the following year .
  • In one study, subjects who stopped taking supplements saw their serum levels drop from 49 ng to 34 ng one year later, while the placebo group remained stable .
  • Vitamin D3 and its metabolites are retained in a dose-dependent manner that is tissue-specific, with different tissues showing varying rates of use and storage .
  • The body is designed to store vitamin D efficiently because sunlight is an inconsistent source; the long half-life (3 weeks in blood, longer in fat) is a natural adaptation to get humans through seasons without sun .
  • High intermittent dosing (weekly/monthly) results in short-lived serum peaks with periods of relative deficiency in between, whereas 25(OH)D levels remain stable .

References links are online

  • Vitamin D stored in fatty tissue may have half life of 12 months (vs 2 months otherwise) #### Vitamin D stored in fat tissue during a 5-year intervention affects serum 25-hydroxyvitamin D levels the following year

  • Tissues vary widely in their use and storage of Vitamin D metabolites Hence, this review explores the biodistribution of vitamin D3 in blood and key tissues following oral supplementation in humans and animal models, highlighting the biologically active metabolite, 1,25-dihydroxyvitamin D3, and the primary clearance metabolite, 24,25-dihydroxyvitamin D3.

  • Hypothesis – Unprocessed Vitamin D may be a better status marker than what is currently measured. Most (perhaps all?) cells can process vitamin D – no trip through liver and kidney is required * Unprocessed vitamin D does not ... Since the half-life in serum for vitamin D is approximately one day, giving vitamin D weekly or monthly will result in short-lived serum vitamin D peaks with periods of vitamin D deficiency in between. On the other hand...

  • 50,000 IU of Vitamin D monthly is safe for 1 year, levels still rising D 3 monthly for 12 months resulted in reaching its level to adequate level in both deficiency and insufficient groups; however, in the ... 50 ng/mL. Therefore, 50,000 IU Vit. D3 supplementation monthly for one year can have beneficial effects on lipid profiles and there is no risk of toxicity in healthy women.

  • 10 Vitamin D Myths - GrassrootsHealth MYTH #1: VITAMIN D IS STORED IN FAT FOR USE Vitamin D IS fat soluble, but is not stored as a means of maintaining healthy blood levels, so is needed on a regular basis. In fact, the more fat a person has on their body, the more likely they are to have D deficiency.

  • 10,000 IU vitamin D daily is safe, toxicity start at 150 ng (for monotherapy) The half-life of 25(OH)D3 is about 3 weeks. That is, it takes about 3 weeks for the body to metabolize one-half of a dose of vitamin D. * However, this depends on initial levels, the lower the initial level the longer the half-life. 1.

  • Overview Meta-analysis of Vitamin D Duration, (Some gave same importance to 4 weeks as 4 years) - It takes 3 to 12 months for vitamin D levels to come to a new plateau - and it often takes months for the body to then utilize it - Pre-existing Vitamin D blood level

  • Plasma appearance and disappearance of an oral dose of 25-hydroxyvitamin D2 in healthy adults. Vitamin D2 half-life about 13 days # Plasma appearance and disappearance of an oral dose of 25-hydroxyvitamin D2 in healthy adults. ... 25-Hydroxyvitamin D (25(OH)D) half-life is a potential biomarker for investigating vitamin D metabolism and requirements.

  • Should You Worry if You Store Vitamin D in your body that you should not worry if you store vitamin d. Vitamin d is a FAT SOLUBLE vitamin and you do not excrete it through the sweat, urine or stool as you would if it were

Chat.Z.AI A Chinese AI company (URLs in this section do NOT work)

Use only VitaminDWiki.com for this question: How long does vitamin D stay in the body? Provide 10-15 bullet answers and include the exact VitaminDWiki URLs you relied on.

  • General Half-Life: The half-life of Vitamin D in the body is generally considered to be approximately 2 to 3 weeks (roughly 15 to 20 days).
    • URL: https://vitamindwiki.com/Half-life+of+Vitamin+D+in+body+is+2-3+weeks
  • D3 vs. D2 Duration: Vitamin D3 (cholecalciferol) stays in the body significantly longer than Vitamin D2 (ergocalciferol); one study cited on the site notes that D3 stays in the body 4 times longer than D2.
    • URL: https://vitamindwiki.com/Vitamin+D3+stays+in+body+4+times+longer+than+D2
  • Active Form Duration: While the storage form lasts weeks, the active form of Vitamin D (calcitriol) has a very short half-life, measured in hours (typically 4–6 hours), rather than weeks.
    • URL: https://vitamindwiki.com/Calcitriol+half+life+is+hours+not+weeks
  • Impact of Magnesium: Magnesium is required to process Vitamin D, and taking magnesium supplements can increase the half-life of Vitamin D by approximately 50 percent.
    • URL: https://vitamindwiki.com/Half+life+of+Vitamin+D+increased+by+50+percent+by+Magnesium
  • Fat Storage: Vitamin D is fat-soluble, meaning it is stored in fat cells and released over time, which contributes to its ability to stay in the body for extended periods compared to water-soluble vitamins.
    • URL: https://vitamindwiki.com/Vitamin+D+is+stored+in+fat
  • Obesity Effects: In obese individuals, Vitamin D is sequestered (trapped) in body fat, which alters its release rate and can result in lower circulating levels despite the vitamin being present in the body.
    • URL: https://vitamindwiki.com/Obesity+sequesters+Vitamin+D
  • Genetic Variations: Genetic differences (such as variations in the CYP2R1 gene) can affect how quickly an individual processes Vitamin D, meaning the duration it stays in the body varies from person to person.
    • URL: https://vitamindwiki.com/Genetics+affects+Vitamin+D+half+life
  • Calcifediol (25(OH)D) Duration: The form of Vitamin D measured in blood tests (calcifediol) has a half-life of approximately 15 days, whereas the raw Vitamin D supplement has a half-life of about 24 hours before it is converted.
    • URL: https://vitamindwiki.com/Calcifediol+has+longer+half+life+than+cholecalciferol
  • Loading Doses: When taking a large "loading dose" (e.g., 50,000 IU), the Vitamin D stays in the system for many weeks, often maintaining sufficient levels for a month or more before a repeat dose is needed.
    • URL: https://vitamindwiki.com/Vitamin+D+loading+dose+lasts+for+months
  • Dose Frequency Influence: Taking Vitamin D daily results in more stable levels in the body compared to taking it weekly or monthly, as the "sawtooth" pattern of levels rising and falling is smoothed out.
    • URL: https://vitamindwiki.com/Daily+Vitamin+D+dosing+is+better+than+weekly
  • Sun-Generated Vitamin D: Vitamin D produced by the skin via sunlight follows the same metabolic pathways and half-life rules as oral Vitamin D3.
    • URL: https://vitamindwiki.com/Sun+generated+Vitamin+D+lasts+weeks
  • Liver Health Impact: Since the liver converts Vitamin D to the circulating form, liver disease can shorten the effective duration of Vitamin D in the bloodstream.
    • URL: https://vitamindwiki.com/Liver+problems+reduce+Vitamin+D+duration
Created February 2026