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The quick answer: most adults do well on 1,000–2,000 IU (25–50 mcg) of vitamin D3 per day for maintenance, rising to 2,000–4,000 IU in dark winter months or with little sun. Always choose D3 (not D2), take it with a fatty meal, and pair it with K2 at higher doses. The calculator below turns your goal, sun exposure and preferred form into a personal dose.
Vitamin D Dosage Calculator (Free): Your Daily IU Target
Top 5 Vitamin D3+K2 Supplements — Tested & Ranked 2026
| Product | Form / Dose | Rating | Price | Best For | Buy |
|---|---|---|---|---|---|
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EDITORS CHOICE Thorne D3+K2 NSF Certified Sport | D3 + MK-7 K2 1000 IU D3 + 200mcg K2 | ★★★★½ 4.8/5 (3,800+) | $34.00 | Arterial + bone health | Amazon ↗ |
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BEST VALUE Life Extension D3 K2 Non-GMO · GMP | D3 + MK-7 K2 5000 IU D3 + 45mcg K2 | ★★★★½ 4.7/5 (4,200+) | $14.00 | High-dose D3 protocol | Amazon ↗ |
|
Jarrow Formulas D3+K2 Non-GMO Verified | D3 + MK-7 K2 2500 IU D3 + 180mcg K2 | ★★★★½ 4.7/5 (3,100+) | $19.99 | Balanced D3/K2 ratio | Amazon ↗ |
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BUDGET PICK NOW Foods D3+K2 GMP · Vegan | D3 + MK-7 K2 1000 IU D3 + 45mcg K2 | ★★★★½ 4.6/5 (5,400+) | $13.99 | Affordable daily combo | Amazon ↗ |
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CLINICAL GRADE Pure Encapsulations D3+K2 NSF · GMP | D3 + MK-7 K2 2000 IU D3 + 90mcg K2 | ★★★★½ 4.8/5 (1,900+) | $36.00 | Sensitive individuals | Amazon ↗ |
Disclosure: NordVital earns a commission on Amazon purchases at no extra cost to you. Rankings based on independent testing, clinical evidence, and third-party lab reports.
The quick answer: most adults do well on 1,000–2,000 IU (25–50 mcg) of vitamin D3 per day for maintenance, rising to 2,000–4,000 IU in dark winter months or with little sun. Always choose D3 (not D2), take it with a fatty meal, and pair it with K2 at higher doses. The calculator below turns your goal, sun exposure and preferred form into a personal dose.
Free Tool
Vitamin D dosage calculator: your daily IU target
Answer three questions and get an evidence-based vitamin D3 dose, whether to add K2, and how to take it.
General guidance based on Endocrine Society and NIH ODS ranges. The only way to dial in your dose is a 25-OH vitamin D blood test. Deficiency correction should be doctor-supervised.
Vitamin D dosage by goal (2026)
| Goal | Daily D3 dose | Add K2? | Notes |
|---|---|---|---|
| General maintenance | 1,000–2,000 IU (25–50 mcg) | Optional | Endocrine Society suggests 1,500–2,000 IU/day for adults |
| Bone & immune | 2,000 IU (50 mcg) | Yes (MK-7) | K2 steers calcium into bone rather than arteries |
| Low winter mood | 2,000–4,000 IU (50–100 mcg) | Yes at 4,000+ | Higher end in the darkest months; retest in spring |
| Correcting deficiency | 4,000 IU (100 mcg) — supervised | Yes | For 25-OH below 20 ng/mL; retest after 8–12 weeks |
1 mcg of vitamin D = 40 IU. The Tolerable Upper Intake Level for adults is 4,000 IU/day without medical supervision. The only way to truly dial in your dose is a 25-OH vitamin D blood test — most experts target 30–50 ng/mL.
How to take vitamin D so it works
Vitamin D3 supplementation is one of the most impactful interventions for general health given how widespread deficiency is. At 1000-4000 IU with K2 and magnesium cofactors, the evidence for immune function, bone density, testosterone support, and mood regulation is very strong. Test your levels first — 70% of people are sub-optimal, most have no idea.
- Always pick D3, not D2. D3 (cholecalciferol) is about 87% more effective than D2 at raising and holding your blood level.
- Take it with a fatty meal. Vitamin D is fat-soluble; food with some fat markedly improves absorption.
- Add K2 (MK-7) at higher doses. Once you take 4,000+ IU, K2 helps direct the extra calcium into bone rather than soft tissue.
- Vegan? Lichen-derived D3 is true D3 and far better than plant D2. Oil-based drops absorb well.
- Test, do not guess. A 25-OH blood test (target ~30–50 ng/mL) is the only way to know your real dose.
Based on Endocrine Society and NIH ODS vitamin D guidance. General education, not medical advice — deficiency correction should be supervised by a doctor.
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