Vitamin

Vitamin D

Also known as: cholecalciferol, D3, ergocalciferol, D2

Evidence

Vitamin D is a fat-soluble hormone and micronutrient essential for calcium absorption, bone health, immune function, and cellular regulation. Most people have insufficient levels and may benefit from supplementation, particularly those with limited sun exposure.

Last reviewed June 2026 · Evidence graded from peer-reviewed research, not editorial opinion. Educational only — not medical advice.

Add Thorne Vitamin D + K2 Liquid to your stack — free

The highest-scored Vitamin D product in our catalog (96/100). Track dose and overlaps in the app.

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Every Vitamin D product we have scored

#	Product	Score	Per serving
1	Thorne Vitamin D + K2 Liquid	96 A	$0.06
2	Momentous Vegan Vitamin D3 5000 IU Supplement	95 A	$0.28
3	Sports Research Vitamin D3 + K2	95 A	$0.40
4	Transparent Labs Grass-Fed Whey Protein Isolate	95 A	$2.00
5	Transparent Labs Vitamin D3 K2	95 A	$0.50
6	Thorne Vitamin D Liquid	94 A	$0.03
7	Thorne Vitamin D-10,000	94 A	$0.43
8	Life Extension Vitamin D3	94 A	$0.13
9	Nordic Naturals Vitamin D3 5000 - Orange	94 A	$0.18
10	Nutricost Calcium Citrate + Vitamin D	93 A	$0.30
11	BulkSupplements Vitamin D3 Softgels	93 A	$0.04
12	Micro Ingredients Vitamin D3 5,000 IU, 500 Softgels	93 A	$0.05

Scored on dose accuracy, form, label transparency and third-party testing. Per-serving cost is list price divided by servings per container. No brand pays to be listed or ranked.

Common questions

How much Vitamin D should I take?

The typical range is 400-4,000 IU daily for maintenance; 1,000-4,000 IU common in supplements. Safe for long-term use; fat-soluble so accumulates in body—monitor levels if taking high doses

When should I take Vitamin D?

Best absorbed with fat-containing meal; timing otherwise flexible. Recommend with dietary fat for optimal absorption.

Which form of Vitamin D is best?

Softgel (oil-based) — Best absorption. Other forms in the catalog: Liquid drops, Spray, Capsule, Liquid, Softgel, Vitamin D3, With K2, D3 liquid, D3 softgels, UV-B device, Cholecalciferol (D3), Ergocalciferol (D2), Calcitriol (active form), D3 (cholecalciferol), D2 (ergocalciferol), capsules, tablets.

Is Vitamin D safe?

Commonly reported: Minimal at recommended doses, Excessive intake (>10,000 IU chronically) may cause hypercalcemia, nausea, weakness.

Which Vitamin D supplement scores highest?

Thorne Vitamin D + K2 Liquid, at 96/100. Scored on dose accuracy, form, label transparency and third-party testing — no brand pays to be listed or ranked.

Daily target & upper limit

20 mcg / day · UL 100 mcg

Vitamin D has an established daily reference intake. See best forms, label synonyms, upper-limit warnings, and top-scoring supplements:

Vitamin D dosage reference →

Primary uses

Bone health
Immune support
Mood regulation
Muscle function
Vitamin D supplementation
Vegan vitamin D source
Bone support
Immune function
Testosterone
Reproductive hormones
Implantation
Male and female fertility

What systematic reviews concluded

Outcomes that systematic reviews of Vitamin D reached a verdict on: 10 with a benefit, 10 with no effect, 6 unclear. Each is quoted from a review and linked to it on PubMed. How these were read.

Reviews found a benefit (10)

Benefitspinal fusion success

“demonstrating a significantly higher likelihood of fusion in patients with better vitamin D status or supplementation” PMID 42675950

Benefitchronic rhinosinusitis severity and recurrence

“Vitamin D deficiency is strongly associated with increased disease severity and recurrence in CRS. Supplementation appears to provide clinical benefits and may serve as a promising adjunct to standard therapy.” PMID 42568492

Benefitsarcopenia-related measures (lean mass, muscle strength, physical function)

“co-supplementation with vitamin D enhanced LM gains (SMD =0.993; 95% CI: 0.112, 1.874; n = 11), muscle strength (SMD =2.005; 95% CI: 0.975, 3.035; n = 11), and physical function (SMD = 3.038; 95% CI: 2.196, 3.879; n = 18) significantly.” PMID 37196876

Every supplement reviewed for muscle strength & mass →

Benefitacute respiratory tract infections

“Vitamin D supplementation was safe and it protected against acute respiratory tract infection overall.” PMID 28202713

Benefitsystemic inflammation in autoimmune disease(as Cholecalciferol)

“Vitamin D3 effectively corrects deficiency and exerts modest, systemic anti-inflammatory effects in autoimmune patients.” PMID 41952022

Every supplement reviewed for inflammation →

Benefitsperm count and motility(as Cholecalciferol)

“Nevertheless, it may contribute to improvements in total sperm count and the percentage of motile sperm, potentially enhancing reproductive function.” PMID 40776878

Every supplement reviewed for testosterone & erectile function →

and 4 more.

Reviews found no effect (10)

No effectpatient-reported outcomes after spinal fusion

“Patient-reported outcomes showed inconsistent results, with no significant effects in random-effects analyses and changes below minimal clinically important differences.” PMID 42675950

No effecttotal testosterone and androgen bioavailability markers

“Current randomized evidence does not demonstrate a statistically clear or reproducible effect of vitamin D supplementation on total testosterone or androgen bioavailability markers in adult men.” PMID 42451097

Every supplement reviewed for testosterone & erectile function →

No effectfractures and falls

“this review found little to no benefits from use of calcium, vitamin D, or combined supplementation on the prevention of fractures and falls.” PMID 42161415

Every supplement reviewed for bone health →

No effectall-cause mortality

“Vitamin D supplementation alone was not associated with all cause mortality in adults compared with placebo or no treatment.” PMID 31405892

No effectserious adverse events

“Vitamin D did not influence the proportion of participants experiencing at least one serious adverse event (adjusted odds ratio 0.98, 0.80 to 1.20, P=0.83).” PMID 28202713

No effectdisease activity markers in autoimmune disease(as Cholecalciferol)

“though its effect on core disease activity markers is limited” PMID 41952022

and 4 more.

Not enough to say: depressive symptoms; cardiometabolic risk factors; cerebral cavernous malformation disease activity; type 2 diabetes incidence; arterial stiffness (pulse wave velocity); falls and fall-related injuries.

11 findings from reviews in specific patient groups (such as cancer, pregnancy or surgery) are not shown here.

How it works

Acts as a hormone regulating calcium and phosphate absorption
Activates vitamin D receptors throughout the body
Modulates immune cell differentiation and function
Supports muscle protein synthesis
Influences neurotransmitter and hormone production

Dosage

Typical range: 400-4,000 IU daily for maintenance; 1,000-4,000 IU common in supplements
Timing: Best absorbed with fat-containing meal; timing otherwise flexible
With food: Recommend with dietary fat for optimal absorption
Duration: Safe for long-term use; fat-soluble so accumulates in body—monitor levels if taking high doses
Special populations: Older adults (50+) may need higher amounts (600-800 IU minimum); dark-skinned individuals in northern climates need more; pregnant/nursing women should discuss dosing with healthcare provider

Forms

Softgel (oil-based)
Liquid drops
Spray
Capsule
Vitamin D3
With K2
D3 liquid
D3 softgels
UV-B device
Cholecalciferol (D3)· 70/100
Ergocalciferol (D2)· 70/100
Calcitriol (active form)· 70/100
D3 (cholecalciferol)· 70/100
D2 (ergocalciferol)· 70/100
capsules· 70/100
tablets· 70/100

Safety

Common side effects

Minimal at recommended doses
Excessive intake (>10,000 IU chronically) may cause hypercalcemia, nausea, weakness

Contraindications

Hypercalcemia or conditions causing elevated calcium
Sarcoidosis and certain granulomatous diseases (vitamin D increases calcium absorption)
Concurrent high-dose calcium supplementation (risk of toxicity)

Products containing Vitamin D

Top-scoring supplements in our catalog that list Vitamin D on the label. Each product is graded on Formulate's ingredient-level rubric — dose accuracy, form, transparency, and third-party testing.

Thorne

Vitamin D + K2 Liquid

Find on Amazon

Momentous

Vegan Vitamin D3 5000 IU Supplement

Find on Amazon

Sports Research

Vitamin D3 + K2

Find on Amazon

Transparent Labs

Grass-Fed Whey Protein Isolate

Find on Amazon

See all products →

Known interactions

Evidence notes

Strong RCT evidence supports vitamin D for bone health, immune function, and reducing deficiency. Extensive observational data supports broader health benefits. Recommended by major health organizations.

Grade A: Multiple well-designed human trials support the main claims.

Cited research for Vitamin D

Clinical studies referenced across Formulate guides that mention vitamin d. Each links to the full study page with PubMed source + the guides that cite it.

Related in Vitamin

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Medical disclaimer. This page is educational and does not replace advice from a qualified healthcare provider. Individual needs and risks vary — consult a professional before starting, stopping, or combining supplements, especially if you are pregnant or nursing, taking medication, or managing a health condition.