Name: Thorne Vitamin D + K2 Liquid
Brand: Thorne

Verdict: BUY. EDE Score 81/100. Thorne Vitamin D + K2 Liquid is a competent oil-based liquid combining D3 and K2 with the convenience of metered drops. The strengths are real: liquid MCT-oil format is one of the most bioavailable D3 delivery systems, the metered dropper enables precise titration from 1,000 to 5,000 IU/day, and the price per effective day is excellent at $0.20. The weakness is the K2 form: Thorne uses MK-4 (half-life around 2 hours) rather than MK-7 (half-life around 72 hours). For systemic K2 effects on bones and arteries, MK-7 has substantially better bioavailability data. This product is also NOT NSF Certified for Sport, unlike Thorne's flagship Vitamin D-5,000 capsule. Strong BUY for adults seeking flexible D3 dosing; not the optimal pick for athletes or for K2-driven bone protocols.

This article contains paid links. We may earn a commission if you purchase through these links. These commissions never influence our scoring.

At a glance

Metric	Value
Brand	Thorne
Product	Vitamin D + K2 Liquid
Form	Liquid drops, oil-based (MCT)
Bottle size	1 fl oz (30 ml)
Servings per bottle	600
Serving size	2 drops
Active ingredients per serving	Vitamin D3 1,000 IU (25 mcg) + Vitamin K2 (MK-4) 200 mcg
Suggested dosing	2 drops, 1 to 3 times daily (1,000 to 3,000 IU D3)
Price (Thorne direct, typical)	$30.00
CPED (at 4,000 IU/day clinical dose)	$0.20 per effective day
Best-in-class CPED for D3+K2	$0.15 to $0.30 (Sports Research, Now Foods)
Third-party certification	Third-party tested (NOT NSF Certified for Sport)
EDE Score	81/100
Verdict	BUY

Why this product matters for men 40+

Vitamin D status is a well-documented modifier of testosterone, bone health, immune function, and mortality risk in men 40+. The 2017 Graz Vitamin D and TT-RCT (NCT01748370) found that 12 weeks of vitamin D3 supplementation at 20,000 IU/week (around 2,860 IU/day) did not raise total testosterone in healthy men with normal baseline testosterone¹. The 2019 follow-up arm of the same trial in men with low baseline testosterone also failed to find a significant testosterone increase from D3 supplementation alone². A 2015 post-hoc analysis of three RCTs (N = 184) at doses of 600 to 2,000 IU/day similarly found no testosterone effect³.

The takeaway is nuanced: vitamin D supplementation is not a reliable testosterone booster in men with adequate baseline status. It is, however, foundational for bone metabolism, calcium absorption, immune function, and (for men with deficiency) measurable improvements in physical performance markers. Most American men 40+ are vitamin D insufficient (25-OH D below 30 ng/mL); about 35 percent are clinically deficient. Correcting that status through daily supplementation with 2,000 to 5,000 IU/day D3 is one of the cheapest, highest-evidence health interventions available.

The K2 question is separate. K2 directs absorbed calcium toward bones and away from arteries. Pairing D3 with K2 is theoretically synergistic: D3 increases calcium uptake, K2 ensures it ends up in the right tissues. The form of K2 matters more than most consumers realize.

Editorial commentary

What we are paying attention to with this product: Thorne built this as a flexibility-first liquid. Two drops equal one nominal serving, and the metered dispenser makes it trivial to scale from 1,000 IU/day (2 drops, maintenance) to 5,000 IU/day (10 drops, repletion of deficiency). This is genuinely useful. Most D3 capsule formats lock you into a single dose; this lets you titrate based on bloodwork.

Where it loses points and we have to be honest: the K2 form. Thorne uses MK-4 (menatetrenone) at 200 mcg per 2-drop serving. MK-4 has a half-life of approximately 2 hours and poor systemic bioavailability at nutritional doses. A 2012 Sato study comparing MK-4 vs MK-7 at 420 mcg single dose found that MK-4 was undetectable in serum at any timepoint while MK-7 was well absorbed and detectable for up to 48 hours⁴. The clinical evidence supporting MK-4 for bone health uses pharmacological doses (45 mg/day, divided across 3 servings), not the 200 mcg nutritional dose in this product.

For the K2 contribution to be meaningfully effective at this dose, MK-7 would have been the more defensible form choice. Thorne's positioning of MK-4 as "the most clinically studied form" is technically true (lots of historical research) but commercially favorable: MK-4 is cheaper to manufacture than MK-7 from natto fermentation. The product still wins on the D3 side, but the K2 side is more about marketing copy than bioavailability.

Second concern: this product is NOT NSF Certified for Sport. Thorne's certification spans 20+ products (including their Vitamin D-5,000 capsule, the Magnesium Bisglycinate powder, and the Zinc Picolinate 30 mg we reviewed earlier). The Vitamin D + K2 Liquid is third-party tested for purity but does not carry the NSF for Sport seal. This matters if you compete in sports under WADA-aligned testing.

What is actually in it

Ingredient	Form	Dose per serving	Clinical effective dose	% of effective dose	Evidence level
Vitamin D3	Cholecalciferol	1,000 IU (25 mcg)	2,000-5,000 IU/day	20-50% (at 1 serving)	Strong
Vitamin K2	Menatetrenone (MK-4)	200 mcg	90-180 mcg/day (MK-7 reference range)	Above MK-7 reference, but bioavailability concern	Moderate (form-dependent)

Other ingredients: Medium chain triglyceride oil, mixed tocopherols.

That is the entire formulation. No fillers, no sweeteners, no flavoring. The MCT oil is functional (improves D3 and K2 absorption since both are fat-soluble) and the mixed tocopherols serve as a natural preservative.

To hit the 4,000 IU/day clinical effective dose for D3 repletion, you need 8 drops (4 servings). To stay at the 1,000 IU/day maintenance level, 2 drops daily is sufficient. The metered dropper makes both regimens easy.

EDE Score breakdown

Criterion	Weight	Score (0-100)	Weighted	Notes
Dose Efficacy	30%	70	21.0	1,000 IU D3 per serving = below 2,000-5,000 IU clinical range. Requires 2-5 servings/day.
Bioavailability	20%	88	17.6	MCT oil liquid is excellent for D3 absorption. K2 as MK-4 has documented poor bioavailability at nutritional doses vs MK-7.
Third-Party Testing	15%	70	10.5	Third-party tested, but NOT NSF Certified for Sport (unlike Thorne's flagship D-5,000 capsule).
Label Transparency	15%	100	15.0	Two-ingredient formulation, full disclosure, no proprietary blend.
Manufacturer Reputation	10%	95	9.5	Thorne clean FDA record, 100+ pro sports teams.
Community Sentiment	5%	50	2.5	Default in Phase 1, enriched Q3 2026.
Price Per Effective Dose	5%	90	4.5	$0.20/day at clinical 4,000 IU dose = top tier.
EDE Score	100%		81 / 100	BUY

See our methodology for the full formula, weights, and tier definitions.

What we like

Liquid MCT-oil format is a genuinely better D3 delivery system. Vitamin D3 is fat-soluble, and MCT oil provides immediate lipid transport. Several studies show oil-based D3 has superior bioavailability compared to dry capsule formulations, particularly in older adults with reduced fat absorption efficiency.
Metered dropper enables flexible titration. The self-dispensing top delivers consistent drops, so you can move smoothly from 1,000 IU/day (maintenance) to 5,000 IU/day (deficiency repletion) based on your 25-OH D bloodwork. Capsule formats lock you into preset doses.
600 servings per 1 fl oz bottle. The math is favorable: at 1 serving (2 drops) per day you get a 600-day supply for $30. Even at 4 servings/day (4,000 IU) you get a 150-day supply, putting CPED at $0.20.
Single-purpose formulation. No proprietary blend, no excipients beyond MCT oil and tocopherols. You know exactly what you are getting.
D3 is in the cholecalciferol form. This is the form your body produces from sun exposure and the form with the strongest bioavailability evidence (vs D2 ergocalciferol, which is roughly 30 percent less effective at raising serum 25-OH D).

What we don't like

K2 form is MK-4, not MK-7. This is the single biggest concern. MK-4 has a half-life of approximately 2 hours and is undetectable in serum at nutritional doses (420 mcg single intake, per Sato 2012)⁴. MK-7 has a half-life of around 72 hours and is well absorbed at much lower doses. For systemic K2 effects on bone osteocalcin activation and arterial calcification protection, MK-7 has substantially better data at supplement-relevant doses. The 200 mcg of MK-4 in this product is below the pharmacological dosing window where MK-4 has demonstrated clinical efficacy (45 mg/day divided).
NOT NSF Certified for Sport. Thorne's Vitamin D-5,000 capsule has the NSF Certified for Sport designation; this liquid does not. If you are an athlete subject to WADA-aligned testing, choose the certified capsule version instead.
Sub-clinical D3 dose at one serving. 1,000 IU per 2 drops is at maintenance level for someone already replete. For D3 deficiency repletion (the more common scenario for men 40+), 4,000 to 5,000 IU/day is the typical clinical regimen, requiring 4 to 5 servings (8 to 10 drops).
Drop-counting is operator-dependent. Multiple user reviews mention difficulty waiting the required 10 to 15 seconds per drop in the metered dispenser, leading some to transfer the oil to a third-party squeeze dropper. The dispenser works, but is not as foolproof as a counted capsule.
Liquid formats are sensitive to storage. Oil-based liquids degrade faster than capsules with heat exposure. Thorne instructs not to refrigerate, but to store cool and dry. If your kitchen runs warm, the bottle is exposed to oxidative stress.

Cost per effective day (CPED)

Bottle price:                       $30.00 (Thorne direct, typical)
Servings per bottle:                600 (2 drops per serving)
Total D3 IU per bottle:             600 servings * 1,000 IU = 600,000 IU
Clinical effective dose per day:    4,000 IU D3 (clinical repletion target)
Days of effective dosing:           600,000 IU / 4,000 IU = 150 days
CPED:                               $30.00 / 150 days = $0.20 per effective day

Thorne Vitamin D + K2 Liquid costs $0.20 per effective day at the 4,000 IU/day clinical repletion dose. At maintenance dose (1,000 IU/day, 2 drops daily), CPED drops to $0.05 per day, with a single bottle lasting almost 2 years.

For comparison, the lowest-CPED tier on our D3+K2 grid is $0.15 to $0.30 per effective day, achieved by Sports Research D3+K2 softgels and Now Foods D3+K2 capsules. Thorne sits inside that tier on price.

The premium some buyers pay for this product is for the metered dropper convenience (titration flexibility) and the Thorne brand. The premium is not for K2 form quality, since the MK-4 in this formulation underperforms MK-7 alternatives at the same price point.

Ingredient-by-ingredient analysis

Vitamin D3 (cholecalciferol)

Dose in this product: 1,000 IU (25 mcg) per 2-drop serving Clinical effective dose: 2,000 to 5,000 IU/day for D3-insufficient adults; 4,000 IU/day is the most-studied repletion dose¹ ² ³ Evidence level: Strong Verdict for this ingredient: Below clinical range at 1 serving, in range at 4 to 5 servings

Vitamin D3 is one of the most-supplemented compounds in the world, and the clinical data is extensive but more nuanced than supplement marketing suggests. Three pillars of evidence are relevant for men 40+:

Bone health. D3 is essential for intestinal calcium absorption. Without adequate D3 status (25-OH D above 30 ng/mL), calcium balance is impaired regardless of dietary intake. The relationship between D3 status and bone mineral density is consistently demonstrated across populations.

Immune function. D3 modulates innate and adaptive immunity through vitamin D receptor expression on immune cells. Multiple meta-analyses link D3 supplementation with reduced respiratory infection incidence, particularly in deficient populations.

Testosterone (the marketing claim). This is where the evidence is weaker than commonly claimed. The 2017 Graz Vitamin D and TT-RCT trial in healthy men found no testosterone increase from 12 weeks of D3 at approximately 2,860 IU/day vs placebo¹. The 2019 follow-up arm in men with low baseline testosterone also failed to find a significant effect². A 2015 Heijboer post-hoc analysis of three trials (combined N = 184) at doses 600 to 2,000 IU/day found no testosterone effect³. The takeaway: do not buy D3 expecting a testosterone boost. Buy D3 for bone, immune, and general status correction.

Mortality. Observational data and several meta-analyses associate vitamin D sufficiency with reduced all-cause mortality, particularly in older adults. The causality is debated, but the safety of supplementation at 2,000 to 5,000 IU/day is well-established.

For our scoring, the dose efficacy criterion is the limiting factor: 1,000 IU per single 2-drop serving is below the 2,000 to 5,000 IU/day clinical range. This is not a label deception; Thorne's directions correctly suggest 2 drops 1 to 3 times daily. It does, however, mean that the per-serving math does not match the per-day clinical dose math.

Vitamin K2 (as menatetrenone, MK-4)

Dose in this product: 200 mcg per 2-drop serving Clinical effective dose: 90 to 180 mcg/day (MK-7 reference); 45 mg/day (pharmacological MK-4 reference) Evidence level: Moderate (form-dependent) Verdict for this ingredient: Form choice is the issue, not the dose

Vitamin K2 directs calcium toward bones and away from soft tissues by activating two key proteins: osteocalcin (in bones) and matrix Gla-protein (in arteries). The clinical question is not whether K2 works; it does. The question is which form delivers usable serum levels at supplement-relevant doses.

The Sato 2012 study in healthy women compared MK-4 and MK-7 at 420 mcg single dose: MK-7 reached maximum serum concentration at 6 hours and was detectable for 48 hours; MK-4 was undetectable at every timepoint⁴. Subsequent 7-day repeat-dosing at 60 mcg/day showed MK-7 accumulation in serum while MK-4 produced no measurable serum increase. The systemic bioavailability of MK-4 at nutritional doses is poor.

The clinical evidence for MK-4 in osteoporosis prevention uses pharmacological doses (45 mg/day, divided), which is 225 times the 200 mcg in this product. At nutritional doses, MK-4 is rapidly cleared and may exert local tissue effects but does not reach the systemic distribution that MK-7 achieves at 100 to 180 mcg/day.

For a D3+K2 stack purchased primarily for systemic K2 effects (bone osteocalcin activation, arterial calcification protection), MK-7 is the form with stronger bioavailability data at the dose ranges typical of supplement formulations. The MK-4 in this product is not useless; it is sub-optimal.

Community sentiment summary

Community sentiment is one signal among seven and is weighted 5% in the EDE Score. In Phase 1 of the DosedWise project, this criterion uses a default neutral score of 50/100. The Reddit Intelligence layer for automated sentiment analysis across r/VitaminD, r/Supplements, r/Nootropics, and r/Testosterone ships in Q3 2026, at which point this section will be replaced with quantitative sentiment data from the past 90 days.

Anecdotal observation across men's-health and bone-health communities: Thorne Vitamin D + K2 Liquid is consistently named as a convenient and well-tolerated D3 delivery system. The most common positive themes are the metered dropper precision and clean ingredient list. The most common negative themes are the K2 form choice (MK-4 vs MK-7 debate is recurring), the slow drop-dispensing mechanism, and the absence of NSF Certified for Sport on this SKU when other Thorne D3 products carry the certification.

This summary is editorial commentary and is not yet weighted into the EDE Score. The score above already accounts for the 5% Community Sentiment weight at the Phase 1 default value.

Compared to alternatives

For D3+K2 combination products, here is how Thorne Vitamin D + K2 Liquid compares to top alternatives we have audited:

Product	Form	K2 Form	EDE Score	CPED	Verdict
Thorne Vitamin D + K2 Liquid	Liquid drops	MK-4	81/100	$0.20	BUY
Sports Research D3+K2 (5,000 IU)	Softgel, coconut oil	MK-7	91/100	$0.18	TOP PICK
Thorne Vitamin D-5,000 (no K2)	Capsule	none	90/100	$0.15	TOP PICK
Now Foods D3+K2 (1,000 IU)	Veg capsule	MK-7	86/100	$0.10	BUY
Pure Encapsulations D3+K2	Capsule	MK-7	84/100	$0.40	BUY
Generic Amazon D3 5000 IU softgel	Softgel	none	60/100	$0.05	WATCH

Thorne wins on liquid format flexibility and brand reputation. Sports Research wins decisively on K2 form (MK-7 vs MK-4) and dose efficacy (5,000 IU vs 1,000 IU per serving), at a comparable CPED. If you need NSF Certified for Sport, Thorne Vitamin D-5,000 capsule (not the liquid) is the go-to. If you want maximum K2 bioavailability and a capsule format, Now Foods or Pure Encapsulations are stronger picks.

Who should buy this

Thorne Vitamin D + K2 Liquid is best for:

Men 40+ who already track their 25-OH D bloodwork and need flexible titration between maintenance (1,000 to 2,000 IU) and repletion (4,000 to 5,000 IU) doses.
Buyers who prefer liquid formats over capsules (faster onset, easier on digestion, no swallowing).
Adults who value the Thorne brand reputation and want a clean, two-ingredient formulation with no proprietary blends.
Stack-builders who already get their K2 from another source (or food: natto, hard cheeses, egg yolks) and treat the K2 in this product as a complementary contribution rather than the primary K2 source.

Thorne Vitamin D + K2 Liquid is NOT for:

Athletes subject to WADA-aligned drug testing. Use Thorne Vitamin D-5,000 capsule (NSF Certified for Sport) instead.
Buyers who specifically need the K2 in their D3 stack to do meaningful systemic work. The MK-4 form at 200 mcg is sub-optimal; choose an MK-7 product instead (Sports Research, Now Foods).
Anyone with high-volume daily supplement routines who finds drop-counting tedious. A capsule or softgel is more practical.
Men taking anticoagulant medications (Coumadin, warfarin). Vitamin K interferes with anticoagulant effect; consult your physician before any K2 supplementation.

Stacking notes

Vitamin D3 + K2 pairs cleanly with the rest of the men's-health basics:

Magnesium glycinate or bisglycinate at 300 to 400 mg/day. Magnesium is a cofactor for vitamin D metabolism. Suboptimal magnesium status reduces the conversion of D3 to its active 1,25-(OH)2 form regardless of how much D3 you supplement.
Zinc bisglycinate or picolinate at 15 to 30 mg/day. Foundational mineral status for men 40+.
Boron citrate at 6 to 10 mg/day. Modulates vitamin D and free testosterone availability.
Standalone MK-7 at 100 to 200 mcg/day if you specifically want robust K2 effects on bone and arterial protection. The MK-4 in this product can stay in your stack as supplementary K2; MK-7 covers the systemic side.

Take this product with a meal that contains some fat. Both D3 and K2 are fat-soluble; the MCT oil in the formulation helps, but co-ingestion with dietary fat further improves absorption. Avoid taking with hot beverages (oxidative stress on the oil base).

If you want the full picture of the men's-health stack, see our best testosterone supplements for men 40+ pillar.

Better alternatives

If Thorne Vitamin D + K2 Liquid does not fit your needs, consider:

Sports Research D3+K2 (5,000 IU + MK-7) (EDE 91/100, CPED $0.18): Coconut oil softgel format, K2 as MK-7 (not MK-4), single-serving 5,000 IU D3 hits clinical repletion dose without multi-drop math. Our pragmatic TOP PICK in the D3+K2 category.
Thorne Vitamin D-5,000 (capsule, no K2) (EDE 90/100, CPED $0.15): If you do not need K2 in the same product (or already get K2 from food/standalone supplement), this is Thorne's NSF Certified for Sport D3 SKU, which the liquid version is not.
Now Foods D3+K2 (1,000 IU + MK-7) (EDE 86/100, CPED $0.10): Cheap, high-bioavailability K2 (MK-7), capsule format. The price-conscious BUY. Lower D3 dose per capsule, so you may need 2 to 4 capsules/day for repletion.

Frequently asked questions

Is Thorne Vitamin D + K2 Liquid worth buying?

Yes, with a caveat about the K2 form. The product scores 81/100 (BUY) on the strength of the liquid MCT-oil delivery format, the metered dropper convenience, the clean two-ingredient formulation, and the excellent CPED of $0.20/day at clinical D3 dose. The caveat is that the K2 is in the MK-4 form, which has documented poor bioavailability at nutritional doses compared to MK-7. If your primary reason for buying a D3+K2 combo is the K2 contribution, this is not the product to choose.

Is the K2 in this product MK-4 or MK-7?

This product uses MK-4 (menatetrenone). Thorne specifically chose MK-4 because, per the brand's marketing language, it is "the most clinically studied form" of vitamin K2. The historical research base for MK-4 in osteoporosis prevention uses pharmacological doses (45 mg/day divided), which is 225 times the 200 mcg in this nutritional supplement. At nutritional doses, MK-7 has substantially better serum bioavailability and a much longer half-life (72 hours vs 2 hours).

Is Thorne Vitamin D + K2 Liquid NSF Certified for Sport?

No. This specific product is third-party tested but does NOT carry the NSF Certified for Sport designation. Thorne's Vitamin D-5,000 capsule (different SKU) does carry the NSF for Sport seal. If you are subject to athletic drug testing under WADA-aligned protocols, choose the certified capsule version instead.

What is the optimal D3 dose for men 40+?

The clinical effective range for D3 repletion in deficient or insufficient adults is 2,000 to 5,000 IU/day, with 4,000 IU/day being the most-studied dose for raising serum 25-OH D into the optimal 30 to 50 ng/mL range. Maintenance dosing in already-replete individuals is 1,000 to 2,000 IU/day. Bloodwork (25-OH D) should guide your specific dose; do not exceed 10,000 IU/day without medical supervision.

Will Thorne Vitamin D + K2 Liquid raise my testosterone?

The published evidence does not support D3 supplementation as a reliable testosterone booster in men with adequate baseline status. The 2017 Graz RCT in healthy men¹, the 2019 follow-up arm in men with low baseline testosterone², and the 2015 Heijboer post-hoc analysis³ all failed to find significant testosterone increases from D3 supplementation alone. D3 is foundational for bone, immune, and general health; do not buy it expecting a testosterone effect.

Can I take this product with prescription medications?

Vitamin K interferes with the action of anticoagulant drugs (Coumadin, warfarin, others). If you take any blood thinner, do not start this product without explicit physician approval. For other medications, the D3 component generally does not interact, but always check with your pharmacist or physician before adding any supplement to a multi-medication regimen.

Where to buy

This product is widely available across US retailers. Pricing as of audit date (2026-05-03):

Thorne direct at the official site. Often ships fastest and is eligible for FSA/HSA via Truemed.
Amazon if you want Prime delivery and already have an Amazon supplement subscription cadence.
iHerb typically competitive on per-bottle price with international shipping options.

Cross-check the price across all three on order day. The CPED math we report above is based on the typical retail price; aggressive iHerb or Vitacost promotions can push the per-bottle cost down further.

Final verdict

BUY: Thorne Vitamin D + K2 Liquid is a competent oil-based D3 delivery vehicle with K2 as a secondary feature that underperforms its marketing claim.

The EDE Score of 81/100 reflects three trade-offs. The strengths are real: liquid MCT format (top-tier D3 bioavailability), metered dropper flexibility, clean formulation, and excellent CPED at the clinical repletion dose ($0.20/day). The weaknesses are also real: K2 in the MK-4 form has poor systemic bioavailability at the 200 mcg nutritional dose used here, the 1,000 IU per serving D3 dose requires multiple servings to hit clinical range, and the product is not NSF Certified for Sport.

Buy this if you want flexible D3 titration via drops and treat the K2 as a complementary contribution rather than the primary K2 source. Skip to Sports Research D3+K2 (5,000 IU + MK-7, EDE 91, CPED $0.18) if you specifically want both the higher per-serving D3 dose and the more-bioavailable K2 form.

If you decide to buy:

Buy direct from Thorne (paid link)
Buy on Amazon (paid link)
Buy on iHerb (paid link)

Methodology and disclosures

This review uses the DosedWise Methodology v1.0. The EDE Score formula is:

EDE Score =
  (Dose Efficacy * 0.30) +
  (Bioavailability * 0.20) +
  (Third-Party Testing * 0.15) +
  (Label Transparency * 0.15) +
  (Manufacturer Reputation * 0.10) +
  (Community Sentiment * 0.05) +
  (Price Per Effective Dose * 0.05)

DosedWise earned no payment from Thorne for this review. We may earn affiliate commissions when readers purchase through links on this page. These commissions never influence scoring. Read our editorial policy.

This article is for educational purposes only and does not constitute medical advice. Always consult a qualified healthcare provider before starting any supplement, especially if you have a medical condition or take prescription medications. This is particularly important for vitamin K2, which interacts with anticoagulant medications.

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

Community Sentiment is set to a default of 50 in Phase 1 of the DosedWise project. This criterion will be enriched with Reddit and forum data via the DosedWise Reddit Intelligence layer in Q3 2026, at which point this review will be revised.

References

Published: 2026-05-03 Last reviewed: 2026-05-03 Next scheduled review: 2026-11-03 (every 6 months minimum) Author: DosedWise Editorial Team

Lerchbaum E, Pilz S, Trummer C, Schwetz V, Pachernegg O, Heijboer AC, Obermayer-Pietsch B. Vitamin D and Testosterone in Healthy Men: A Randomized Controlled Trial. J Clin Endocrinol Metab. 2017 Nov 1;102(11):4292-4302. PubMed PMID: 28938446. 12-week RCT in 98 healthy men with normal baseline testosterone found no testosterone increase from D3 supplementation at 20,000 IU/week vs placebo. ↩ ↩² ↩³ ↩⁴
Lerchbaum E, Trummer C, Theiler-Schwetz V, Kollmann M, Woelfler M, Heijboer AC, Pilz S, Obermayer-Pietsch B. Effects of vitamin D supplementation on androgens in men with low testosterone levels: a randomized controlled trial. Eur J Nutr. 2019 Dec;58(8):3135-3146. PubMed PMID: 30460609. Follow-up Graz arm in men with low baseline testosterone also failed to find a significant testosterone effect from D3 supplementation. ↩ ↩² ↩³ ↩⁴
Heijboer AC, Oosterwerff M, Schroten NF, Eekhoff EM, Chel VG, de Boer RA, Blankenstein MA, Lips P. Vitamin D supplementation and testosterone concentrations in male human subjects. Clin Endocrinol (Oxf). 2015 Jul;83(1):105-10. PubMed PMID: 25557316. Post-hoc analysis of three RCTs (combined N = 184) at doses 600 to 2,000 IU/day found no testosterone effect. ↩ ↩² ↩³ ↩⁴
Sato T, Schurgers LJ, Uenishi K. Comparison of menaquinone-4 and menaquinone-7 bioavailability in healthy women. Nutr J. 2012 Nov 12;11:93. PMC3502319. Single-dose 420 mcg administration: MK-7 reached peak serum at 6 hours and was detectable up to 48 hours; MK-4 was undetectable at every timepoint. 7-day repeat dosing at 60 mcg/day confirmed MK-4 produces no measurable serum increase at nutritional doses. ↩ ↩² ↩³