Best Vitamin D Supplements (2026): Science-Backed Picks

Vitamin D deficiency is staggeringly common. An estimated 42% of American adults have insufficient vitamin D levels, with rates even higher among people with darker skin, older adults, and those living in northern latitudes. Given how important this vitamin is for bone health, immune function, mood, and muscle strength, supplementation makes sense for a large portion of the population.

The good news: vitamin D supplements are cheap, effective, and well-studied. The bad news: there are hundreds of options, and the differences between them actually matter. Here are our top three picks, and why.

For a deeper dive into dosing, testing, and food sources, read our guide on how much vitamin D you actually need.

Our Top Picks at a Glance

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Best Value: Nutricost Vitamin D3 5000 IU

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If you just need a reliable, no-frills vitamin D3 supplement, Nutricost is absurdly good value. At $0.04 per serving — four cents — a single bottle lasts eight months. That’s roughly $20/year for daily vitamin D supplementation.

Each softgel delivers 5,000 IU (125mcg) of vitamin D3 in a simple formulation: cholecalciferol in soybean oil inside a gelatin softgel. The product is third-party tested by an ISO-accredited laboratory, and Nutricost has a solid reputation for delivering exactly what the label claims.

The only notable downside is the soybean oil carrier. While the amount is tiny, it’s worth noting for people with soy allergies. And unlike our other picks, there’s no K2 included — if you want the D3+K2 synergy, you’ll need to add K2 separately or upgrade to Sports Research.

Who it’s for: Anyone who wants effective, verified vitamin D at the lowest possible cost. The obvious choice for budget-conscious supplementation.

Best D3+K2 Combo: Sports Research D3 + K2

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This is our overall top recommendation for most people. The combination of 5,000 IU vitamin D3 with 100mcg of vitamin K2 (as MK-7) addresses the most common concern with high-dose D3 supplementation: calcium metabolism.

Here’s why K2 matters: vitamin D increases calcium absorption from the gut. That’s good — you need calcium. But without adequate K2, that calcium can end up deposited in arteries and soft tissues rather than bones. K2 activates proteins that direct calcium to where it belongs. The D3+K2 combo is widely considered the gold standard approach.

Sports Research uses coconut oil as the carrier fat (instead of soybean oil), which some evidence suggests improves absorption of fat-soluble vitamins. The product is USP Verified — one of the most rigorous third-party certifications available — and Non-GMO Project Verified.

At $0.32 per serving, it’s 8x the cost of Nutricost, but you’re getting K2, a better carrier oil, and USP verification. For most people, that’s worth the upgrade.

Who it’s for: Most people. If you’re choosing one vitamin D supplement and want the most evidence-based option, this is it.

Best Liquid / Most Flexible: Thorne D/K2 Liquid

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Thorne’s liquid drops offer something the others can’t: precise dose control. Each drop delivers 1,000 IU of D3 and 200mcg of K2, and you can take 1-5 drops depending on your needs. This is ideal for people who have had their blood levels tested and want to dial in an exact dose.

Thorne is a practitioner-grade brand with NSF Certified for Sport status, meaning every batch is independently verified for purity, potency, and absence of banned substances. This is the vitamin D that professional athletes, Olympic competitors, and informed practitioners trust.

The liquid format also works well for people who have difficulty swallowing pills, or for adding to food or beverages.

At $0.42 per drop (and most people need 2-5 drops), this is the most expensive option. You also need to be careful with dosing — it’s easier to accidentally over- or under-dose with drops than with pre-measured softgels. Store it properly (cool, dark place) to maintain potency.

Who it’s for: Athletes, people who’ve tested their levels and want precise dosing, anyone who struggles with pills, or those who want the highest level of third-party certification.

Buyer’s Guide: Choosing a Vitamin D Supplement

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D3 vs. D2

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Always choose D3 (cholecalciferol). It’s the form your body produces naturally from sunlight, and research consistently shows it’s more effective at raising and maintaining blood levels of 25-hydroxyvitamin D. D2 (ergocalciferol) is the plant-derived form and is less potent per IU.

The one exception: strict vegans may prefer D2 or a lichen-derived D3, since standard D3 comes from lanolin (sheep’s wool oil).

Why K2 Matters

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Vitamin K2 (specifically the MK-7 form) works synergistically with D3 by activating osteocalcin (which deposits calcium in bones) and matrix GLA protein (which prevents calcium from depositing in arteries). This isn’t just theoretical — observational studies suggest that adequate K2 intake is associated with reduced cardiovascular calcification.

If you take more than 2,000 IU of D3 daily, pairing it with K2 is a smart move.

How Much to Take

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The answer depends on your current blood levels:

• Below 20 ng/mL (deficient): Work with your doctor. You may need a higher loading dose (e.g., 50,000 IU weekly for 8-12 weeks).
• 20-30 ng/mL (insufficient): 2,000-5,000 IU daily typically corrects this over 2-3 months.
• 30-50 ng/mL (sufficient): 1,000-2,000 IU daily for maintenance.
• Above 50 ng/mL: You likely don’t need to supplement, but monitor levels.

Factors that increase your needs: darker skin, obesity, limited sun exposure, living above 37th parallel (roughly north of Atlanta), older age, and malabsorption conditions.

Testing Your Levels

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A simple blood test for 25-hydroxyvitamin D tells you where you stand. Most labs consider 30-50 ng/mL optimal. The Endocrine Society recommends at least 30 ng/mL. Get tested before supplementing, then retest after 3 months to confirm your dose is appropriate.

Frequently Asked Questions

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How much vitamin D should I take daily?

Most adults benefit from 1,000-5,000 IU daily, depending on sun exposure, skin color, latitude, and current blood levels. Get a blood test to determine your specific needs.

Should I take vitamin D3 with K2?

It’s a good idea, especially at doses above 2,000 IU daily. K2 helps ensure calcium goes to your bones rather than your arteries.

What is the difference between D2 and D3?

D3 is significantly more effective at raising blood levels and is the preferred form. D2 is plant-derived and less potent per IU.

Can you take too much vitamin D?

Toxicity is rare but possible at very high doses (above 10,000 IU daily for extended periods). Symptoms include nausea, weakness, and elevated calcium. Regular blood testing is the best safeguard.

When should I take vitamin D?

With your largest meal containing fat, since D3 is fat-soluble and absorbs better with dietary fat.