Thorne
Thorne Vitamin D/K2 Liquid
Vitamin D3 paired with K2 for better calcium absorption and bone health.
Best for
Adults who spend limited time outdoors, live in northern climates, or have been told by their doctor they have low vitamin D levels.
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Our Verdict
Vitamin D deficiency affects over 40% of American adults, and the problem gets worse with age. Thorne's D/K2 liquid pairs D3 with K2 — K2 directs calcium to bones rather than arteries, making the combination more effective than D3 alone for bone health.
What We Like
- D3 + K2 combo improves calcium absorption
- Liquid form — easy to adjust dose
- NSF Certified for Sport — no fillers
- Thorne is trusted by professional athletes
- Small dropper dose — easy to take
Watch Out For
- Liquid form requires careful dosing
- Slightly higher cost than basic D3 capsules
Why D3 + K2?
Vitamin D increases calcium absorption, but without K2, that calcium can deposit in arteries rather than bones. K2 (specifically MK-7) activates proteins that direct calcium to bones and teeth and away from soft tissues. The combination is more effective for bone health than D3 alone.
Testing Your Levels
A simple blood test (25-hydroxyvitamin D) tells you your current level. Optimal range is generally considered 40–60 ng/mL. Many doctors check this as part of routine bloodwork. If you're deficient, supplementation can make a significant difference in energy, mood, and bone health.
Dosing
The liquid form allows precise dosing. Most adults need 2,000–5,000 IU of D3 daily, depending on their baseline levels and sun exposure. Start with the standard dose and adjust based on bloodwork. Take with a fat-containing meal for best absorption.
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