How much vitamin D do adults need per day?

The US Recommended Dietary Allowance is 600 IU (15 mcg) a day for adults up to age 70 and 800 IU (20 mcg) after 70. The upper limit for adults is 4,000 IU (100 mcg) a day.

Should I get my vitamin D level tested?

The 2024 Endocrine Society guideline suggests against routine 25(OH)D testing in healthy people without a specific reason, because trials have not shown that testing improves outcomes. Your clinician may test if you have a condition or risk factor that calls for it.

What blood level of vitamin D is enough?

The US Food and Nutrition Board considers 20 ng/mL (50 nmol/L) or more sufficient for most people, and notes that levels above 50 ng/mL (125 nmol/L) may be linked to adverse effects. Some experts, including Rhonda Patrick, favor higher targets; the 2024 guideline found no clear evidence for an optimal level.

How much does 1,000 IU raise vitamin D levels?

Rhonda Patrick gives a rule of thumb of about 5 ng/mL per 1,000 IU a day. Responses vary with starting level, age and other factors, so treat it as a rough estimate.

Is D3 better than D2?

Most evidence suggests D3 raises and keeps blood levels higher than D2, especially with large intermittent doses. Both are well absorbed.

Does vitamin D prevent cancer, heart disease or fractures?

This page makes no such claim. In the VITAL trial, 2,000 IU a day for about 5 years did not lower rates of invasive cancer, major cardiovascular events or fractures in generally healthy midlife and older adults.

Can you take too much vitamin D?

Yes. Toxicity, almost always from supplements, can cause high blood calcium with nausea, vomiting, weakness and kidney stones, and in extreme cases kidney failure. Stay within the upper limit unless a clinician advises otherwise.

How Much Vitamin D Should You Take? Intakes, Testing and What Trials Show

For most adults, the US Recommended Dietary Allowance is 600 IU (15 mcg) a day, rising to 800 IU (20 mcg) after age 70, and the upper limit is 4,000 IU, according to the NIH Office of Dietary Supplements. A 2024 Endocrine Society guideline suggests against routine blood testing in healthy people and against taking more than these amounts to prevent disease in healthy adults under 75. Popular advice, including Rhonda Patrick’s, goes further; this page sets out where the evidence and that advice differ.

This page is general information, not medical advice. It makes no claims that vitamin D prevents or treats any disease. If you have a medical condition, are pregnant, take medicines, or have been told your level is low, follow your clinician’s advice.

Recommended intakes and blood levels

Measure	Value	Source
RDA, adults 19–70	600 IU (15 mcg) per day	NIH ODS
RDA, adults over 70	800 IU (20 mcg) per day	NIH ODS
Upper limit, adults	4,000 IU (100 mcg) per day	NIH ODS
Blood level sufficient for most people	20 ng/mL (50 nmol/L) or more	Food and Nutrition Board, via NIH ODS
Risk of deficiency rises below	12 ng/mL (30 nmol/L)	Same
May be linked to adverse effects	Above 50 ng/mL (125 nmol/L)	Same

Blood levels are measured as 25-hydroxyvitamin D, or 25(OH)D. Note the two units: ng/mL and nmol/L differ by a factor of about 2.5.

What the 2024 Endocrine Society guideline says

The guideline panel looked for randomized trials of extra vitamin D in people without a specific medical reason to take it. Its main suggestions:

Healthy adults under 75: it suggests against vitamin D above the current intake recommendations to lower disease risk.
Specific groups: it suggests extra vitamin D for children and adolescents aged 1 to 18, adults 75 and older, pregnant people, and people with high-risk prediabetes. These are clinical decisions to make with a clinician.
Testing: it found no trial evidence supporting routine 25(OH)D screening, including in people with obesity or darker skin, and suggests against routine testing.
Target levels: it found no clear evidence defining an optimal blood level for disease prevention.
How to take it: for people over 50 who need it, it suggests daily doses rather than occasional large doses.

The panel said optimal doses remain unclear because trial doses varied widely.

What large trials found

Trial	Who	Dose	Result
VITAL, 2019	25,871 US men 50+ and women 55+	2,000 IU/day, median 5.3 years	No lower incidence of invasive cancer or major cardiovascular events vs placebo
VITAL fractures, 2022	Same trial	2,000 IU/day	No significant effect on total, nonvertebral or hip fractures

The fracture study’s participants were not selected for low vitamin D or low bone mass, and the results did not change by baseline blood level. These trials tested whether extra vitamin D helps generally healthy people. They do not address correcting a diagnosed deficiency, which is a separate clinical question.

What Rhonda Patrick recommends, and how it compares

On the Huberman Lab episode, Patrick cites observational studies to argue that levels “seem to be ideal between 40 to 60 nanograms per milliliter.” She encourages measuring your level. Her rule of thumb: “taking 1000 IUs of vitamin D will raise blood levels by around five nanograms per milliliter.” She says she takes 5,000 IU a day and her levels hover around 50 ng/mL.

Topic	Rhonda Patrick	Guideline and NIH view
Testing	Measure your level	No routine testing in healthy people
Target	40–60 ng/mL	20 ng/mL is enough for most; above 50 ng/mL may carry risk; no proven optimal level
Dose	About 1,000 IU per 5 ng/mL needed; she takes 5,000 IU	RDA 600–800 IU; upper limit 4,000 IU

Her personal dose is above the upper limit, and the top of her target range is above the level the Food and Nutrition Board links to possible adverse effects. If you want to follow a higher-dose approach, do it with a clinician who can check your calcium and vitamin D levels.

How much does a dose raise blood levels?

A 2019 meta-analysis of 136 articles found a clear dose-response relationship, with the starting level and age as significant factors. Its estimated intakes to reach 30 ng/mL (75 nmol/L) varied widely by region and age, from about 729 IU a day for North American adults to 2,519 IU for European adults aged 18 to 64. Because responses vary, single rules of thumb are rough guides.

D3 or D2?

A meta-analysis of head-to-head trials found D3 raised 25(OH)D more than D2, with a clear difference for large intermittent doses but not for daily dosing. The NIH agrees that D3 tends to raise and keep levels higher, although both forms are well absorbed.

Who is more likely to run low?

The NIH fact sheet names several higher-risk groups: older adults, breastfed babies, people who get little sun, people with darker skin, people with obesity or past gastric bypass surgery, and anyone with a condition that reduces fat absorption. Season, cloud cover and sunscreen also affect how much vitamin D skin makes. The NIH also notes that UV exposure is the most preventable cause of skin cancer and that federal agencies advise sun protection, so sun is not a risk-free way to raise vitamin D. For daylight and the body clock, see the morning sunlight protocol.

Safety

According to the NIH, vitamin D toxicity is almost always caused by supplements. It causes high blood calcium, which can lead to nausea, vomiting, muscle weakness, excessive thirst and kidney stones, and in extreme cases kidney failure and heart rhythm problems. Cases have come from manufacturing errors, products taken in excessive amounts, and incorrect prescriptions. Vitamin D can also interact with some medicines, so mention it to your pharmacist.

For other supplements with stronger evidence, see the evidence-based supplements guide, and for omega-3 doses, the omega-3 fish oil protocol.