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Updated: 2026-05-29 · v2.0 · Prof. G. Pkhakadze, MD, MPH, PhDCiteEditorial
📰Read the full Vitamin D evidence review on GMJ News →Complete clinical article, references and updates on news.gmj.ge. This page is the structured safety summary.
1
Safe
Vitamin D
Cholecalciferol (D3)
Generally SafeStrongFat-Soluble Vitamins
RDA
600 IU
Target
30–50 ng/mL
Upper limit
4,000 IU
Products
3,552
Dosage by population group — reference
🔗 Best with: Vitamin K2 (MK-7), Calcium, Magnesium✅ USP Verified, NSF Contents Certified
⚠ Granulomatous diseases (sarcoidosis, TB) — unregulated extra-renal CYP27B1 can cause life-threatening hypercalcemia even at standard doses [2][21]
⚠ CKD stage 3–5 — standard D3 is ineffective; use calcitriol or alfacalcidol under nephrology guidance [23]
⚠ Thiazide + vitamin D — monitor calcium every 3–6 months for hypercalcemia [9][21]
🥗 Food first — build your daily 600 IU
Check the foods you regularly eat — the bar fills toward your daily target.
Cod liver oil (1 tsp / 5 mL)450 IU
Salmon, wild (85 g cooked)570 IU
Rainbow trout, farmed (85 g cooked)645 IU
Sardines, canned (85 g)164 IU
UV-exposed mushrooms (85 g)366 IU
Fortified milk (240 mL)120 IU
Egg yolk (1 large)44 IU
Fortified orange juice (240 mL)100 IU
0 mcg
Check your regular foods above
☑ Risk checker
Above 37°N latitude
Dark skin (Fitzpatrick IV–VI)
BMI >30
Age over 65
Daily sunscreen use
Little/no oily fish
Malabsorption (IBD, coeliac)
Interacting medications
Select factors
🔬 Lab interpreter
<12
12–20
20–50
50–100
>150
Enter 25(OH)D in ng/mL
Test: Serum 25-hydroxyvitamin D [25(OH)D]. Target: 30–50 ng/mL (75–125 nmol/L) [21]
⚕ For professionals — confirm ranges against your local laboratory.
Clinical verdict
Check 25(OH)D in all at-risk patients (BMI >30, age >65, dark skin, northern latitude) [21]. D3 is 87% more potent than D2 at raising serum levels [4]. Prescribe with a fat-containing meal for optimal absorption [7]. Co-supplement with K2 (MK-7) for bone and vascular benefit [17]. Target 30–50 ng/mL; >50 rarely adds benefit and >150 risks toxicity [1][21]. Large bolus dosing (>300,000 IU) paradoxically increases falls — use daily/weekly dosing [11][25]. The VITAL trial showed no cancer or CVD prevention at 2,000 IU/day but did reduce autoimmune disease by 22% [12][13].
1 How much do I need?
👤 Adults: 600 IU/day (15 mcg) [1]
IOM RDA of 600 IU covers 97.5% of healthy adults assuming minimal sun exposure [1]. Endocrine Society recommends 1,500–2,000 IU/day for adults at risk of deficiency to maintain 25(OH)D >30 ng/mL [21
👴 Elderly: 800–1,000 IU/day [1][21]
Cutaneous synthesis capacity declines 75% by age 70 compared with young adults [2]. The IOM increased the RDA to 800 IU/day for adults >70 [1]. A meta-analysis of 12 RCTs (n = 42,279) found that 700
🤰 Pregnancy: 600–2,000 IU/day [1][21]
👦 Pediatric: Specific dosage data under clinical review
🏃 Athletes: 1,000–2,000 IU/day [21]
Some sports medicine guidelines suggest targeting 25(OH)D 40–60 ng/mL for musculoskeletal performance and injury prevention, though RCT evidence for performance enhancement remains limited [21]. Str
⚖️ Obesity: 2–3× standard dose (1,200–3,000 IU/day) [22]
Vitamin D is sequestered in adipose tissue due to its lipophilic nature, creating a larger volume of distribution. A dose-response study (n = 17,614) found that each unit increase in BMI was associate
🩺 Renal: Calcitriol 0.25–0.5 mcg/day or alfacalcidol 0.25–1.0 mcg/day for CKD stages 3–5 [23]
Standard cholecalciferol may be ineffective in advanced CKD because impaired renal 1α-hydroxylase (CYP27B1) cannot convert 25(OH)D to active calcitriol [23]. KDIGO 2017 guidelines recommend treating
🌱 Vegan: Same as general population: 600–2,000 IU/day [1][21]
D3 from lichen (Cladonia rangiferina) is the only plant-sourced cholecalciferol; bioequivalent to animal-derived D3 [4]. D2 (ergocalciferol) is derived from UV-irradiated yeast/fungi but is 87% less p
⚠️ Conditions: Specific dosage data under clinical review

Deficiency correction

Week 1–8
50,000 IU/wk
Maintenance
1,500–2,000/d
Recheck 3mo
25(OH)D
Target
30–50

How to take

🍽 Timing: Take with the largest meal of the day containing ≥11 g fat for maximum absorption (50% increase vs fasting) [7].
💊 With food: Must be taken with fat-containing food. Oil-based softgels are 30–50% more bioavailable than dry tablets [7]. Pair with avocado, olive oil, nuts, or fatty fish [7].
🚫 Avoid: Separate from cholestyramine/colestipol by ≥4 hours [9]. Separate from orlistat by ≥2 hours [9].
2 Common questions
How much sun exposure is needed for adequate vitamin D production? ▼
Approximately 10–15 minutes of midday sun exposure (10 AM – 3 PM) on arms and legs without sunscreen, 2–3 times per week, is sufficient for fair-skinned individuals at latitudes below 37° during summer months [2]. Individuals with dark skin may require 3–6 times longer [2]. This produces approximately 10,000–20,000 IU in a single session [2]. Above 37°N latitude, UVB is insufficient for synthesis during winter months (November–February) [3].
Is it possible to take too much vitamin D? ▼
Yes, but toxicity is rare and requires sustained intake well above the tolerable upper level. The UL is 4,000 IU/day for adults [1]. Toxicity symptoms (hypercalcemia) typically occur at serum 25(OH)D >150 ng/mL, usually from sustained intake >10,000 IU/day for months [9]. Sun exposure cannot cause toxicity because the skin photodegrades excess previtamin D3 [2]. Single bolus doses >300,000 IU are associated with adverse effects and should be avoided [25].
Which form should I take — D3 or D2? ▼
D3 (cholecalciferol) is preferred. A systematic review of 10 RCTs (n = 1,016) found D3 is 87% more effective than D2 at raising and maintaining serum 25(OH)D [4]. D3 also has a longer half-life (15–18 days vs 10–13 days for D2) [18]. D2 remains an option for vegans who cannot source lichen-derived D3 [4].
Should I take vitamin D with vitamin K2? ▼
Co-supplementation with K2 (MK-7) is recommended by many clinicians when taking vitamin D long-term, particularly for bone and cardiovascular health. K2 activates osteocalcin and matrix Gla protein, directing calcium to bone and away from arterial walls [17]. While large RCTs confirming synergy are pending, the physiological rationale is strong and safety profile excellent [17].
Can I get enough vitamin D from food alone? ▼
For most people, no. Very few foods naturally contain significant amounts [9]. Even a vitamin D-rich diet (fatty fish 2–3 times/week, fortified dairy daily) typically provides 200–400 IU/day — below the RDA of 600 IU [1][8]. Supplementation or adequate sun exposure is needed for most individuals, especially at northern latitudes, in winter, or with dark skin [2][9].
3 Clinical evidence

Strong

Bone mineral density maintenance and fracture prevention when combined with adequate calcium intake (WHI trial, n = 36,282) [10]. Prevention of rickets in children and osteomalacia in adults [1]. Reduced risk of acute respiratory tract infections (IPD meta-analysis, 25 RCTs, n = 11,321; OR 0.88, 95% CI 0.81–0.96; strongest in deficient subjects: OR 0.58) [11]. Autoimmune disease risk reduction by 22% (VITAL trial, n = 25,871, HR 0.78) [12]. HIGH

Moderate

Colorectal cancer risk reduction of 17% per 10 ng/mL increase in serum 25(OH)D, based on pooled data from 17 cohorts (n = 12,813 cases, n = 10,999 controls) [14]. Fall risk reduction of 19% (OR 0.81) in elderly with 700–1,000 IU/day (meta-analysis, 12 RCTs, n = 42,279) [26]. Depression symptom improvement in deficient individuals (effect size moderate, evidence heterogeneous) [27]. MODERATE

Insufficient

Weight loss: no statistically significant effect in VITAL or other large trials [13]. Cognitive decline prevention: VITAL-MIND sub-study (n = 12,167) found no benefit at 2,000 IU/day over 5.3 years [13]. Cardiovascular disease prevention: VITAL primary analysis (n = 25,871) showed no reduction in major cardiovascular events (HR 0.97, 95% CI 0.85–1.12) [13]. Overall cancer mortality: D-Health trial (n = 21,315) found no significant reduction with 60,000 IU/month (HR 0.96, 95% CI 0.80–1.15) [20]. Autier 2014 umbrella review concluded that low vitamin D is a marker of ill health rather than a cause for most extraskeletal outcomes [24]. LOW

Landmark trials

VITAL (Vitamin D and Omega-3 Trial) (2019) n=25871 · RCT, 2×2 factorial, 5.3-year follow-up
No reduction in invasive cancer (HR 0.96) or major cardiovascular events (HR 0.97) [13]
D-Health Trial (2022) n=21315 · RCT, 5-year follow-up, Australia
No reduction in all-cause mortality (HR 0.96) or total cancer (HR 1.00) [20]
WHI Calcium + Vitamin D Trial (2006) n=36282 · RCT, 7-year follow-up, postmenopausal women
Hip fracture HR 0.88 (NS overall); 29% reduction in adherent subgroup (HR 0.71, 95% CI 0.52–0.97) [10]

Key meta-analyses

Martineau AR, et al. 2017 25 trials, n=11321
Vitamin D supplementation reduced risk of acute respiratory infection (OR 0.88, 95% CI 0.81–0.96). Greatest benefit in participants with baseline 25(OH)D <25 nmol/L (OR 0.58) and daily/weekly (not bolus) dosing [11].
Bischoff-Ferrari HA, et al. 2009 12 trials, n=42279
Fall prevention with 700–1,000 IU/day: 19% risk reduction (OR 0.81, 95% CI 0.71–0.92). Doses <700 IU/day did not reduce falls [26].
Bolland MJ, et al. 2018 81 trials, n=53537
Vitamin D supplementation did not prevent fractures (RR 1.00 total, 0.99 hip, 0.98 fall) in unselected community-dwelling adults. Authors concluded routine supplementation is not justified for fracture prevention [25].
Autier P, et al. 2014 trials, n=
Low 25(OH)D associated with many health outcomes in observational studies, but intervention trials showed limited benefit. Concluded low vitamin D may be a consequence rather than a cause of ill health for most extraskeletal outcomes [24].
Palacios C, et al. 2019 30 trials, n=7033
Vitamin D in pregnancy reduced preeclampsia (RR 0.48), gestational diabetes (RR 0.51), and low birth weight (RR 0.55). Combined D + calcium may increase preterm birth risk [15].
4 Safety, toxicity & adverse events

Absolute contraindications

✕ Hypercalcemia (serum calcium >10.5 mg/dL) [9]
✕ Hypervitaminosis D (serum 25(OH)D >150 ng/mL) [9]
✕ Known hypersensitivity to cholecalciferol or ergocalciferol [9]

Relative

⚠ Granulomatous diseases (sarcoidosis, tuberculosis, histoplasmosis) — risk of unregulated calcitriol production causing hypercalcemia; use only under supervision with frequent calcium monitoring [2][21]
⚠ Primary hyperparathyroidism — vitamin D may worsen hypercalcemia; correct surgical indication first [21]
⚠ History of calcium-containing kidney stones — monitor 24-hour urine calcium; keep supplement dose ≤1,000 IU/day unless supervised [10]
⚠ Severe renal impairment (CKD stage 4–5) — standard D3 may not convert to active form; use calcitriol or analogues under nephrology guidance [23]
⚠ Williams syndrome — increased sensitivity to vitamin D causing idiopathic infantile hypercalcemia [21]

🚩 Red flags

● Taking more than 4,000 IU/day without medical supervision exceeds the IOM tolerable upper intake level [1]
● Symptoms of hypercalcemia: nausea, vomiting, confusion, excessive thirst, polyuria, constipation [2][9]
● Known history of kidney stones (nephrolithiasis) or nephrocalcinosis — vitamin D increases urinary calcium excretion [10]
● Granulomatous diseases (sarcoidosis, tuberculosis, some lymphomas) — unregulated extra-renal 1α-hydroxylase may cause hypercalcemia [2][21]
● Concurrent thiazide diuretic use — reduced renal calcium excretion compounds hypercalcemia risk [9]
● Serum 25(OH)D consistently above 100 ng/mL (250 nmol/L) without medical indication [9]
● Concomitant high-dose calcium supplementation (>1,500 mg/day) increases cardiovascular and renal stone risk [10]
● Rapid correction of severe deficiency with large bolus doses (>300,000 IU) may paradoxically increase fall and fracture risk [25]
5 Interactions

Drug interactions

Thiazide diuretics (hydrochlorothiazide, chlorthalidone) Major
Mechanism: Thiazides reduce renal calcium excretion. Combined with vitamin D-enhanced intestinal calcium absorption, serum calcium can rise to dangerous levels [9][21].
Effect: Hypercalcemia: nausea, confusion, cardiac arrhythmias, renal impairment [9].
Action: Monitor serum calcium every 3–6 months when combining [21]. Avoid vitamin D doses above 1,000 IU/day without calcium monitoring [9].
Digoxin (cardiac glycosides) Major
Mechanism: Vitamin D increases intestinal calcium absorption. Elevated serum calcium sensitizes the myocardium to digoxin, lowering the threshold for toxicity [9].
Effect: Digoxin toxicity: arrhythmias (bradycardia, AV block, ventricular tachycardia), nausea, visual disturbances [9].
Action: Monitor serum calcium and digoxin levels closely [9]. Keep serum calcium within normal range (8.5–10.5 mg/dL) [9].
Corticosteroids (prednisone ≥7.5 mg/day, dexamethasone) Moderate
Mechanism: Corticosteroids impair intestinal calcium absorption, increase renal calcium excretion, and accelerate vitamin D catabolism via CYP24A1 induction [21][29].
Effect: Reduced vitamin D efficacy. Accelerated bone loss. Steroid-induced osteoporosis affects 30–50% of long-term users [21].
Action: Patients on chronic corticosteroids (≥3 months) require 1,000–2,000 IU/day vitamin D plus 1,000–1,200 mg calcium [21]. Monitor 25(OH)D and bone density (DEXA) annually [21].
Orlistat (Xenical, Alli) Moderate
Mechanism: Orlistat inhibits pancreatic lipase, reducing dietary fat absorption by approximately 30% [9]. Vitamin D is fat-soluble and co-absorbed with dietary fat [7].
Effect: Reduced vitamin D absorption by up to 30% [9]. Risk of deficiency with long-term use [9].
Action: Take vitamin D at least 2 hours before or after orlistat [9]. Consider higher doses (1,000–2,000 IU/day) [21]. Monitor 25(OH)D annually [21].
Cholestyramine, colestipol (bile acid sequestrants) Moderate
Mechanism: Bile acid sequestrants bind fat-soluble vitamins in the intestinal lumen, preventing micellar incorporation and absorption [9].
Effect: Reduced vitamin D absorption [9]. Risk of deficiency with chronic use [9].
Action: Take vitamin D at least 4 hours before or 1 hour after bile acid sequestrants [9].
Phenytoin, phenobarbital, carbamazepine (CYP450 inducers) Moderate
Mechanism: Potent CYP3A4 and CYP24A1 inducers that accelerate hepatic catabolism of both 25(OH)D and 1,25(OH)2D [9][29].
Effect: Reduced serum 25(OH)D levels by 25–70% [9]. Increased risk of osteomalacia with long-term anticonvulsant use [9].
Action: Monitor 25(OH)D every 6–12 months [21]. Higher vitamin D doses (2,000–4,000 IU/day) may be required to maintain adequate levels [21].

Supplement synergies

Vitamin K2 (MK-7) · 100–200 mcg MK-7/day [17]
K2 activates osteocalcin (directs calcium to bone) and matrix Gla protein (prevents arterial calcification) [17]. Without K2, vitamin D-mobilized calcium may deposit in soft tissues rather than bone [17].
Magnesium · 200–400 mg/day elemental magnesium [1]
Required cofactor for CYP2R1 and CYP27B1 — the enzymes that convert vitamin D to 25(OH)D and then to active calcitriol [2][29]. Magnesium deficiency impairs vitamin D metabolism at both hydroxylation steps [2].
Calcium · 500–1,000 mg/day from diet + supplements (total <1,500 mg/day) [1][10]
Vitamin D enhances intestinal calcium absorption from 10–15% (without D) to 30–40% (with adequate D) [2]. Co-supplementation required for fracture prevention [10].
Omega-3 fatty acids · 1,000–2,000 mg EPA+DHA/day [7]
Fat-soluble vitamin D absorption is enhanced when taken with omega-3 oil capsules providing a fat vehicle [7].

Caution combining

High-dose calcium (>1,500 mg/day)
Combined with vitamin D, excess calcium increases nephrolithiasis risk (WHI: HR 1.17) [10] and may increase cardiovascular risk at very high intakes [10].
High-dose vitamin A (>10,000 IU/day retinol)
Vitamin A antagonizes vitamin D-mediated intestinal calcium absorption and may counteract bone-protective effects [1].
6 Regulatory
United States (FDA): Dietary supplement (DSHEA 1994). GRAS as food additive for fortification. Prescription calcitriol for CKD. UL 4,000 IU/day [1][9].
European Union (EFSA): Authorized health claims for bone, muscle, immune function, and teeth (Regulation 432/2012). UL 4,000 IU/day for adults (EFSA 2012) [5]. Maximum fortification levels set by member states [30].
Japan (MHLW): Dietary supplement. Upper limit 4,000 IU/day (100 mcg). Listed in Japanese Dietary Reference Intakes (2020) [5].
Australia / New Zealand (TGA/FSANZ): Schedule 2 (pharmacy-only) above 1,000 IU/tablet. Listed medicine for doses up to 1,000 IU. Fortification permitted in margarine (mandatory) and selected dairy [5].
7 US supplement products
3,552
on-market products containing Vitamin D (NIH DSLD)

Brands carrying Vitamin D (796)

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8 Frequently paired with
Calcium 2,457 sharedMagnesium 2,029 sharedVitamin C 2,002 sharedZinc 1,862 sharedVitamin E 1,826 sharedFolate 1,673 shared
9 Cite this page
Vancouver: Pkhakadze G. Vitamin D — safety profile [Internet]. Tbilisi: PHIG; 2026 [cited 2026 Jun 16]. Available from: https://supplement.ge/ingredients/vitamin-d/
APA 7th: Pkhakadze, G. (2026). Vitamin D — Safety profile. Public Health Institute of Georgia. https://supplement.ge/ingredients/vitamin-d/
📋 Editorial information
Author: Prof. G. Pkhakadze, MD, MPH, PhD
Affiliation: David Tvildiani Medical University (DTMU)
First published: January 2026
Last reviewed: 2026-05-29
Next review: December 2026
References: 30 cited sources
COI: SupplementIndex receives no funding from supplement manufacturers. All content independently authored by PHIG.
Process: Systematic literature review
📄 License & reuse
Published under Creative Commons Attribution 4.0 International (CC BY 4.0). You may share and adapt for any purpose with attribution.
Pkhakadze G. "Vitamin D — Safety Profile." SupplementIndex, PHIG, 2026. https://supplement.ge/ingredients/vitamin-d/ CC BY 4.0.
GP
Prof. G. Pkhakadze, MD, MPH, PhD
Professor of Public Health · Head of Department, DTMU
Editor-in-Chief, Georgian Medical Journal (ISSN 3088-4322)
Chair, Public Health Institute of Georgia · UEMS Public Health Section
Educational and public health purposes. CC BY 4.0. Consult your healthcare provider before starting any supplement. Corrections: info@accreditation.ge. Publisher: PHIG