How Much Vitamin D Should You Take? The Evidence-Based Answer

Quick Answer✓ Yes

How much vitamin D should I take?

2,000-5,000 IU of vitamin D3 daily for most adults. The official RDA (600 IU) is too low to reach optimal blood levels of 40-60 ng/mL. Always choose D3 over D2 (87% more effective). Get a blood test to know your starting level.

2,000-5,000 IU D3 daily for most adults
D3 is 87% more effective than D2
Get 25-OH vitamin D blood test first
Take with a fatty meal for better absorption

Read full explanation

The official RDA for vitamin D is 600 IU for adults under 70. But almost every vitamin D researcher thinks that number is too low. Some by a lot. Here's what the evidence actually supports and how to figure out your ideal dose.

The Dose Most People Need

2,000-5,000 IU of vitamin D3 daily is what most people need to reach optimal blood levels of 40-60 ng/mL. The official 600 IU prevents rickets but doesn't get most people to the levels associated with broader health benefits.

A large study published in the Journal of Clinical Endocrinology found that 1,000 IU daily raised levels by about 10 ng/mL. If you're starting at a typical deficient level of 20 ng/mL, you need 2,000-4,000 IU to reach 40-60 ng/mL.

Factors that increase your need: darker skin, obesity, limited sun exposure, living above 35th latitude (basically anywhere north of Atlanta), being over 65, and spending most time indoors.

Quick Tips

→Get a 25-OH vitamin D blood test to know your starting level
→Take D3 with a fatty meal for 50% better absorption
→Retest after 3 months of supplementation

D3 vs D2: This Matters

Always take D3 (cholecalciferol), not D2 (ergocalciferol). D3 raises blood levels 87% more effectively than D2. This isn't subtle. D2 is the plant-derived form. D3 is what your skin makes from sunlight. Your body handles D3 much better.

Most prescription vitamin D is D2 (because it's cheaper). If your doctor prescribed D2, ask about switching to D3. The evidence clearly favors it.

Can You Take Too Much?

The upper limit is officially 4,000 IU daily, though many researchers consider up to 10,000 IU safe for short-term use when treating deficiency.

Vitamin D toxicity is real but rare. It generally requires sustained intake above 10,000 IU daily for months. Symptoms: nausea, kidney stones, calcium buildup.

The safest approach: test your levels, supplement based on your actual number, retest after 3 months. Don't just guess at a dose indefinitely.

Key Takeaways

2,000-5,000 IU of D3 daily for most adults. Get tested. Take with fat. Use D3, not D2. Retest in 3 months. It's one of the simplest, cheapest, and most impactful supplements you can take.