Quick answer
Adults need 15 mcg (600 IU) of vitamin D a day up to age 70 and 20 mcg (800 IU) after that, counting food, drinks and supplements. The same 15 mcg applies in pregnancy and while breastfeeding. Adults should stay under 100 mcg (4,000 IU) a day unless a doctor advises more.1,2
Key facts
- Breastfed babies need a 10 mcg (400 IU) vitamin D supplement every day.1
- Most Americans get only 4 to 5 mcg a day from food and drink.2
- VITAL, the largest US trial, tested 50 mcg (2,000 IU) of vitamin D3 a day, half the adult upper limit.1,3
- The Daily Value on labels is 20 mcg (800 IU), so a 50 mcg serving shows as 250% of the Daily Value.2
Recommended amounts by age
| Age or stage | mcg a day | IU a day |
|---|---|---|
| Birth to 12 months | 10 mcg | 400 IU |
| 1 to 18 years | 15 mcg | 600 IU |
| 19 to 70 years | 15 mcg | 600 IU |
| 71 years and older | 20 mcg | 800 IU |
| Pregnant or breastfeeding | 15 mcg | 600 IU |
Breastfed babies should be given a vitamin D supplement of 10 mcg (400 IU) each day, because breast milk alone does not provide enough.1,2
For babies the figure is an adequate intake, a best estimate made because the evidence could not pin down a firm requirement. From age 1 it is a recommended dietary allowance, set to cover nearly all healthy people and to keep bones and calcium levels normal.2
Converting IU and mcg
For vitamin D, 1 mcg equals 40 IU. So 10 mcg is 400 IU, 15 mcg is 600 IU, 50 mcg is 2,000 IU and 100 mcg is 4,000 IU.2
| IU | mcg | How it compares for an adult |
|---|---|---|
| 400 IU | 10 mcg | Two thirds of the 15 mcg most adults need |
| 600 IU | 15 mcg | The amount for adults aged 19 to 70 |
| 800 IU | 20 mcg | The amount from 71, and the label Daily Value |
| 1,000 IU | 25 mcg | A quarter of the upper limit |
| 2,000 IU | 50 mcg | Half the upper limit, and the amount VITAL tested |
| 4,000 IU | 100 mcg | The adult upper limit |
| 5,000 IU | 125 mcg | Above the adult upper limit |
Food labels must list vitamin D in mcg and may also show the IU amount. The Daily Value used on labels is 20 mcg (800 IU) for adults and children aged 4 and older.2
Why the targets assume little sun
The recommended amounts were set on the assumption that people get little sun. Sun is one reason blood levels are usually higher than food intake alone would predict.2
Average intakes from food and drink are about 5.1 mcg (204 IU) a day for men and 4.2 mcg (168 IU) for women, and more than 9 in 10 Americans get less than 10 mcg a day from food alone.2
In 2015 to 2016, 28% of Americans aged 2 and older took a supplement containing vitamin D, rising to 49% of men and 59% of women aged 60 and older. Supplements lifted average intake from 4.8 mcg (192 IU) to 19.9 mcg (796 IU) a day.2
Put together, food alone leaves most people a third of the way to their target, and sunlight or a supplement covers the rest. Someone who works indoors through a northern winter leans on supplements and fortified food far more than someone outdoors in summer.2,4
Body fat holds on to vitamin D, which is one reason people with a higher body weight tend to have lower blood levels and may need more vitamin D to reach the same level.2
Is more than the recommendation better?
VITAL, the largest US trial of vitamin D, gave 2,000 IU of vitamin D3 a day or a placebo to 25,871 adults (men 50 and over, women 55 and over) for a median of 5.3 years. Most already had adequate levels: only 12.9% started below 20 ng/mL.2,3
The Endocrine Society's 2024 guideline suggests against taking more than the recommended intake for healthy adults aged 19 to 74, and against routine blood testing. It suggests supplements for children and teens, adults 75 and older and during pregnancy, without recommending a specific dose.2,5
In VITAL, five years of 2,000 IU a day lifted blood levels but gave adults who already had enough no measurable extra gain over placebo. So 2,000 IU a day is a sound way to avoid running low if you get little sun or have tested low. For a healthy adult under 75 who already has enough, current guidance does not back taking that much for extra benefit.3,5
Upper limits
The upper limit for adults and children aged 9 and over is 100 mcg (4,000 IU) a day from all sources, including during pregnancy and breastfeeding. It is 25 mcg (1,000 IU) for babies up to 6 months, 38 mcg (1,500 IU) from 7 to 12 months, 63 mcg (2,500 IU) at ages 1 to 3 and 75 mcg (3,000 IU) at ages 4 to 8. Signs of toxicity are unlikely below 250 mcg (10,000 IU) a day, but NIH notes that even intakes below the upper limit might cause harm over time.1,2
In 2013 to 2014, an estimated 3.2% of US adults took supplements containing 100 mcg (4,000 IU) or more of vitamin D a day.2
A doctor may prescribe more than the upper limit for a while to correct a low level. That is treatment with follow-up blood tests, not a daily routine to copy.1
If you take more than one of our products, add up the vitamin D. Our Vitamin D3 softgel (50 mcg) and our immune formula (40 mcg) come to 90 mcg a day before food. Men's Multi (10 mcg) on top reaches the 100 mcg limit, and Ashwagandha Complex (20 mcg) on top goes past it.1
What's in ours
What’s in ours
- Vitamin D3: Vitamin D-3, 50 mcg (2,000 IU) per serving, from the label
- Men's Multi: Vitamin D, 10 mcg per serving, from the label
- Ashwagandha Complex: Vitamin D3, 20 mcg per serving, from the label
- Immune Support: Vitamin D3, 40 mcg per serving, from the label
Questions people ask
How much vitamin D3 should a woman take per day?
The same as a man: 15 mcg (600 IU) a day from age 19 to 70, including during pregnancy and breastfeeding, and 20 mcg (800 IU) from 71. The upper limit is 100 mcg (4,000 IU). Our guide for women covers pregnancy, breastfeeding and the years after menopause.1
Is 2,000 IU of vitamin D3 a day too much?
Not for most adults. It is 50 mcg, half the 100 mcg upper limit, and VITAL found no more side effects than placebo over about five years. It is more than the 600 to 800 IU recommended, so it makes most sense if you get little sun or your level has tested low.1,3
See what we make
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Sources
- Office of Dietary Supplements, National Institutes of Health. Vitamin D: Fact Sheet for Consumers. Updated November 8, 2022. Opened 2026-10-07.
- National Institutes of Health, Office of Dietary Supplements. Vitamin D: Fact Sheet for Health Professionals. Updated June 27, 2025. Opened 2026-10-07.
- Manson JE, et al. Vitamin D Supplements and Prevention of Cancer and Cardiovascular Disease. N Engl J Med. 2019;380(1):33-44. Opened 2026-10-01.
- Heaney RP, et al. Human serum 25-hydroxycholecalciferol response to extended oral dosing with cholecalciferol. Am J Clin Nutr. 2003;77(1):204-210. Opened 2026-10-07.
- Demay MB, et al. Vitamin D for the Prevention of Disease: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2024;109(8):1907-1947. Opened 2026-10-01.
This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.