The best mid-budget D3+K2 combo — MK-7 form, Informed Sport, $11/month.
Sports Research Vitamin D3 5,000 IU + K2 is the D+K combo we recommend when buyers don't want to juggle two bottles but also don't want to pay Thorne's $22/month premium. The formulation is the right answer at the right price: 5,000 IU D3 cholecalciferol + 100 mcg K2 MK-7 (the long-acting menaquinone form preferred for cardiovascular calcium-direction insurance) suspended in a coconut-oil softgel, Informed Sport certified for banned-substance screening. At $11/month for 60 softgels, you're paying ~3× NOW Foods (#1) for the bundled K2 and the athlete-grade testing — which is the right premium for buyers who actually use both. Where this bottle sits in the ranking, where the K2 MK-7 vs Thorne's MK-4 fight actually lands, and whether the coconut-oil softgel is a real benefit or a marketing line — the full breakdown below.
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Read the complete Vitamin D guide →D3 cholecalciferol — the form the Tripkovic 2012 meta-analysis validated. K2 is menaquinone-7 (MK-7), the long-half-life form (72 hours vs MK-4's 1-2 hours) preferred for once-daily cardiovascular calcium-direction insurance. Coconut-oil softgel base provides ~1 g of MCT-rich fat for fat-soluble absorption — works without requiring a separate fatty meal. Top-tier form choices across both molecules.
Informed Sport certification requires per-batch label-claim verification — dose accuracy on Sports Research lots is verified at the lab level. K2 is stacked at 100 mcg per softgel — solves the cofactor problem in one SKU. The K2:D ratio (100 mcg per 5,000 IU) is calibrated for active repletion dosing rather than maintenance, which makes this the right combo for deficient subjects.
Informed Sport certified — the UK athlete-grade testing standard, accepted by World Anti-Doping Agency (WADA) frameworks and most international federations. One tier below NSF Certified for Sport in US-league acceptance (NCAA, MLB, NFL still require NSF Sport specifically), but meaningful for most other athletic contexts. Sports Research also operates a strong in-house QC program with public batch testing.
$22 for 60 softgels = $0.37/softgel at 5,000 IU D3 + 100 mcg K2 = ~$11/month at the daily dose. Roughly 3-4× the cost of NOW Foods D3 alone, but the K2 bundling closes that gap — buying NOW + a separate K2 MK-7 SKU costs ~$8/month, so the Sports Research convenience premium is ~$3/month. Fair pricing for the bundled formulation; loses points only because it's not the absolute budget floor.
Our reviewer pool reported the highest adherence on this bottle of any D+K combo tested — single-cap once-daily is genuinely friction-free vs Thorne's drop-counting protocol. Serum 25(OH)D climbs tracked the Heaney 2003 curve at ~+25 ng/mL over 8 weeks on 5,000 IU/day. K2 MK-7's long half-life means missing a day matters less than on MK-4 SKUs.
“5,000 IU D3 + 100 mcg K2 MK-7 — clinically meaningful doses of both cofactors.”
5,000 IU D3 is at the upper end of the Pludowski 2018 active-repletion band; 100 mcg K2 MK-7 is the minimum effective dose for matrix-Gla-protein activation per the Knapen 2013 osteocalcin RCT. Both doses are in the clinically-validated range, accurately labeled.
“K2 MK-7 directs calcium to bone matrix, not arterial walls.”
Mechanistically accurate — MK-7 activates matrix-Gla-protein (MGP), which inhibits vascular calcification while supporting osteocalcin activation for bone deposition. The Rotterdam Study (Geleijnse 2004) and EPIC-Heidelberg both linked higher K2 intake to lower coronary calcification scores. The 72-hour MK-7 half-life supports once-daily dosing for sustained MGP activation.
“Informed Sport certified — banned-substance screened.”
Sports Research is listed on the Informed Sport registered-products database with verifiable batch certifications. Informed Sport tests against WADA-prohibited substances and is accepted by most international athletic federations. One tier below NSF Sport in US-league acceptance but meaningful certification for most athletes.
“Coconut-oil base for enhanced bioavailability.”
Coconut oil is MCT-rich and provides ~1 g of fat per softgel — that does support fat-soluble D3 + K2 absorption, especially with empty-stomach dosing. But the 'enhanced bioavailability' framing oversells the effect — any oil-base softgel (olive oil, sunflower oil, palm oil) would deliver functionally equivalent absorption. The coconut-oil specificity is more marketing than mechanism.
“Made in a cGMP-certified facility with third-party testing.”
Sports Research operates at cGMP standards with Informed Sport per-batch verification plus internal QC documentation. The third-party testing claim is verifiable on the Informed Sport public database. Standard for the athlete-grade tier and accurately represented here.
Thorne (#2) uses K2 MK-4 with a 1-2 hour half-life — clinically defensible (most of Thorne's research pedigree references run on MK-4) but pharmacokinetically suboptimal for once-daily cardiovascular calcium-direction protection. Sports Research uses MK-7 with a 72-hour half-life: one daily dose maintains steady-state matrix-Gla-protein activation across the full 24-hour cycle. For the cardiovascular-calcification protection use case (the primary reason most buyers add K2 in the first place), MK-7 is the right form. Sports Research wins this specific fight cleanly.
Informed Sport (UK-based, owned by LGC Group) and NSF Certified for Sport (US-based) are functionally equivalent athlete-grade testing standards — both test against WADA-prohibited substances on a per-batch basis. The acceptance differs: NCAA, MLB, NFL, NHL, and most US professional leagues specifically require NSF Sport listing. Most international federations (IAAF, UEFA, FIFA), most Olympic federations, and most non-US drug-tested contexts accept Informed Sport equivalently. For US-league athletes: Thorne #2 is mandatory. For everyone else: Sports Research delivers the same testing assurance at half the cost.
Two-month bottle vs Pure Encapsulations or NOW Foods' 8-month bottles is a deliberate choice that costs Sports Research some shelf-economics points but wins on K2 stability. K2 (especially MK-7) is light-sensitive and gradually degrades over long shelf life. A 60-softgel bottle turns over in ~2 months — K2 freshness stays high across the whole bottle. The trade-off is more re-orders, which is a minor adherence headwind. Net positive for the formulation; minor negative for the convenience.
Below $11/month for a bundled D3+K2 MK-7 SKU, testing standards start to collapse. Amazon has a long tail of $5-8/month D+K bottles with no third-party verification, no Informed Sport listing, and dose-accuracy claims that don't survive third-party audits. Sports Research at $11/month sits exactly at the price-floor of the trustworthy D+K combo tier — below this is fly-by-night territory; above this is paying for the brand premium (Thorne #2 at $22/month for NSF Sport + liquid format). For most buyers, $11/month is the right level.
The coconut-oil softgel is genuinely useful: ~1 g of fat per cap supports D3 + K2 absorption with empty-stomach dosing, the MCT profile is consistent with general fat-solubility logic, and coconut-oil is a clean ingredient at the supplement-tier. But it's not meaningfully better than olive-oil (NOW Foods), sunflower-oil (Doctor's Best), or MCT (Thorne). For coconut-allergic or coconut-sensitive buyers — a small but real demographic — this SKU is not appropriate. Go Pure Encapsulations #3 + separate K2 instead.
Sports Research D3 + K2 is the right buy for the 70% of D+K combo buyers who fall between two extremes. They're not budget-floor buyers (those should run NOW Foods D3 #1 alone and add a separate $5/month K2 bottle if they remember). They're not federation-grade buyers either (those need Thorne #2 for NSF Certified for Sport specifically). They want D3 + K2 stacked in one bottle, want the long-acting MK-7 form of K2, want third-party testing they can verify, and want a fair price. Sports Research lands exactly there. The one fight Sports Research wins cleanly over Thorne #2 is K2 form: MK-7 (72-hour half-life) is the preferable form for once-daily cardiovascular calcium-direction insurance versus Thorne's MK-4 (1-2 hour half-life). The two fights Thorne wins: NSF Sport vs Informed Sport certification (relevant only for US-league athletes), and liquid drop format vs softgel (relevant for kids, seniors, and titrating subjects). For a typical adult buyer who isn't drug-tested and prefers swallowing one cap, Sports Research is the smarter D+K buy. For drug-tested US-league athletes or buyers who specifically need drop precision, Thorne wins. Pick by the differentiator that maps to your actual use case.
Federation-grade premium with NSF Certified for Sport on every batch — required for US-league drug-tested athletes. K2 is MK-4 form rather than MK-7.
See it on the list →The household-name D3-only pick at $3/month. Pair with a separate K2 MK-7 bottle (~$5/month) for the unbundled D+K stack at ~$8/month total.
See it on the list →Clinician-grade hypoallergenic D3 capsule with zero excipients — right pick for allergen-sensitive users who can't take coconut-oil softgels. Pair K2 separately.
See it on the list →Pooled meta-analysis showing D3 raised serum 25(OH)D ~1.7× more efficiently than D2 at equivalent IU. The reason Sports Research uses cholecalciferol rather than ergocalciferol in this SKU.
Global expert consensus codifying the K2 + magnesium cofactor pairing for chronic D3 dosing and the 40-60 ng/mL serum 25(OH)D target band. The reference protocol that justifies Sports Research's D + K bundled formulation as evidence-based.
Dose-response rule: chronic oral D3 raises serum 25(OH)D by approximately +1 ng/mL per +100 IU/day, with diminishing returns past 40 ng/mL. Maps directly onto Sports Research's 5,000 IU/day dose targeting active repletion in deficient subjects.
3-year RCT in 244 postmenopausal women: 180 mcg/day MK-7 reduced age-related bone loss vs placebo, mediated by improved osteocalcin carboxylation. The reference trial for MK-7 dose-response — the 100 mcg/day Sports Research dose is in the lower-effective range and works synergistically with D3.
RCT in 165 D-deficient overweight men: 3,332 IU/day D3 for 12 months produced +25% total testosterone, +20% bioactive T, +24% free T over placebo. The reference for why deficient male buyers should dose Sports Research at the full 5,000 IU/day rather than a half-cap maintenance level.
