Thorne Vitamin D3/K2 Liquid

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Thorne Vitamin D3/K2 Liquid

Pharmaceutical-grade D3 + K2 (MK-4) liquid drops. NSF Certified.

Thorne Vitamin D3/K2 Liquid

★★★★☆4.9 / 5 rating
500 IUD3
100 mcgK2
Liquid dropsForm
NSFCert.
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Thorne Vitamin D3/K2 Liquid

Prices change often, so we link straight to the retailer instead of quoting one. We earn a commission from purchases through these links, at no cost to you.

Pharmaceutical-grade D3 + K2 (MK-4) liquid drops. NSF Certified.

What is Thorne Vitamin D3/K2 Liquid?

Thorne Vitamin D3/K2 Liquid is part of our editor-vetted catalog of premium supplements. Our research team reviews each formula’s third-party testing, clinical research, and value to bring you transparent, evidence-based recommendations.

At a Glance

  • D3: 500 IU
  • K2: 100 mcg
  • Form: Liquid drops
  • Cert.: NSF

How We Researched This Product

Our editorial team evaluates every product against criteria including: ingredient quality and bioavailability, third-party testing (USP, NSF, ConsumerLab), dosage compared to clinical research, brand reputation and manufacturing standards, value per serving, and customer feedback patterns.

Where to Buy

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Important Notes

Educational content — not medical advice. Consult a qualified healthcare provider before adding any supplement to your routine, especially if you take prescription medication or have a medical condition.

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Scientific References
  • 1Holick MF, et al. (2011). Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. PMID 21646368
  • 2Pilz S, et al. (2011). Effect of vitamin D supplementation on testosterone levels in men. Horm Metab Res. PMID 21154195
  • 3Martineau AR, et al. (2017). Vitamin D supplementation to prevent acute respiratory infections: systematic review and meta-analysis. BMJ. PMID 28202713
  • 4Autier P, et al. (2014). Vitamin D status and ill health: a systematic review. Lancet Diabetes Endocrinol. PMID 24622671

All studies are peer-reviewed and sourced from PubMed/NCBI. This article is for informational purposes only and does not constitute medical advice. Consult a qualified healthcare provider before starting any supplement regimen.

❓Frequently Asked Questions
For most healthy adults, the recommended intake is 600 IU (15 mcg) a day, or 800 IU (20 mcg) after age 70 (NIH Office of Dietary Supplements). The 2024 Endocrine Society guideline found no added benefit above that for most people aged 19–74, and suggests extra vitamin D only for children and teens, adults over 75, pregnancy and high-risk prediabetes. Up to 4,000 IU (100 mcg) a day stays within the adult upper limit. If a blood test shows a deficiency, your doctor will set a higher, supervised dose for a limited time.
Fatigue, bone and muscle aches, frequent illness, depression (particularly seasonal), hair loss, and slow wound healing are the most common. However, most people with deficiency have no obvious symptoms until tested. The only definitive test is a 25-hydroxyvitamin D blood test (25-OH D). Levels of 20 ng/mL (50 nmol/L) or more are sufficient for most people, and levels above 50 ng/mL (125 nmol/L) can be associated with adverse effects (NIH ODS). Routine testing is not recommended for healthy adults (Endocrine Society, 2024).
Always D3 (cholecalciferol) — it's 87% more potent at raising and maintaining 25-OH levels compared to D2 (ergocalciferol). D3 is the form your skin makes from sunlight and the form found in fatty fish. D2 is derived from plants/fungi and is less bioavailable. Most prescriptions use D2 for historical reasons; over-the-counter D3 is superior.
Not strictly necessary for vitamin D's immune, muscle, and mood benefits. However, K2 (MK-7 form) works synergistically with D3: it activates osteocalcin (which directs calcium into bones) and matrix GLA protein (which prevents calcium from depositing in arteries). At higher D3 doses (4,000+ IU), some experts suggest adding K2 (90–200 mcg MK-7), although the evidence is still limited.
Only a few foods are rich in it. NIH figures: cooked sockeye salmon about 570 IU per 3 oz, farmed rainbow trout about 645 IU, one egg about 44 IU, canned light tuna about 40 IU per 3 oz, and fortified milk about 120 IU per cup. Fatty fish and fortified foods make the 600–800 IU target reachable. Sunlight also makes vitamin D in your skin, but how much depends on season, latitude, time of day and skin type.