how much time in the sun for vitamin D

Vitamin D Equivalent versus Sun Exposure Time

I wanted to know the equivalent amount of sunlight on the skin that’s the same as (similar to) a vitamin D supplement in IU (International Units).

Why? Because I know how very important vitamin D is for our Immune System Health!

There are many benefits of vitamin D. You can look it up. Here’s one interesting study (I heard about this before, but you might be interested)…

“A systematic review and meta-analysis of 14 observational studies that included a total of 31,424 adults (mean age ranging from 27.5 to 77 years) found an association between deficient or low levels of 25(OH)D and depression [source: British Journal Psychiatry]

Most People Do Not Get Enough Vitamin D

It’s estimated that more than 40% of American adults have a vitamin D deficiency [source: NIH National Library of Medicine].

It’s estimated as many as half of all children, teens and young adults are vitamin D deficient, as are as many as 25 to 57 percent of American adults [source: Lee]

This deficiency is very common and on the rise.

Why People Don’t Get Enough

Many reasons for this include:

  • Partly due to vigilant sun protection, since sunscreen with SPF 30 reduces vitamin D production by 95%.
  • The majority of people in the United States (for example) do not get any vitamin D from the sun at all, during the winter months. Zero. Exceptions at southern latitudes.
  • In the U.S., nearly everyone is deficient while living above 37 degrees north of the equator — in the U.S., that’d put you north of Washington, D.C. and north of the Utah/Arizona border.
  • One’s skin pigment (the darker your skin), the less UVB rays can penetrate.
  • Overweight and Obesity. Vitamin D is fat-soluble. The more fat cells your body has, the more at risk of a deficiency, because the vitamin becomes trapped in those fat cells.
  • Most people are “inside” most of the day in our modern world.
  • Kids don’t “play outside” like they used to.
  • Although one needs to be cautious of overdoing sun exposure (given the well known risks), many people are seemingly petrified of the sun these days…
  • Age. As we get older, it naturally becomes more difficult to convert sunlight into D3. For example, when exposed to the same amount of UVB radiation, a person who is 70 years old will make 75 percent less D3 than a 20-year-old.

How Much Vitamin D?

Since 2010, the recommended daily allowance (RDA) of vitamin D falls between 600 and 800 International Unit (IU) per day (based on age).

But more recent research suggests adults may actually need at least 2,000 IU of vitamin D every day to maintain a healthy level in the body and reap the most benefits [source: MayoClinicHolick].

I take plenty of vitamin D supplement during the Fall-Winter-Spring months. But I’m curious how much I might get naturally from the sun during the summer months.

Personally, I take 5,000 IU per day. That is not medical advice. It’s simply what I do.

How vitamin D gets into your body from the sun

The simple explanation: 

The sunshine vitamin is made from cholesterol in your skin when it’s exposed to the sun.

When your skin is exposed to sunlight, it makes vitamin D from cholesterol.

The sun’s ultraviolet B (UVB) rays hit cholesterol in the skin cells, providing the energy for vitamin D synthesis to occur.

~ healthline

The technical detailed explanation:

When UVB rays hit your skin, a chemical reaction happens:

Your body begins the process of converting a prohormone in the skin into vitamin D. In this process, a form of cholesterol called 7-dehydrocholesterol (7-DHC), naturally found in your skin, absorbs the UVB radiation. It gets converted into cholecalciferol. Cholecalciferol is the previtamin form of D3.

Next, the previtamin travels through your bloodstream to your liver, where the body begins to metabolize it. It turns into hydroxyvitamin D, which is also known as 25-hydroxyvitamin D or 25(OH)D.

The kidneys then convert the 25(OH)D into dihydroxyvitamin D, also called 1,25-dihydroxyvitamin D or 25(OH)2D. This is the hormone form of vitamin D your body can use.

[sources: The George Mateljan FoundationHolick]

Vitamin D produced from the skin can last at least twice as long as the vitamin D you take in through foods or supplements. 

From a study in Norway, “Under picture-perfect conditions, the human body is able to produce as much as 10,000 IU to 20,000 IU of vitamin D3 in just 30 minutes.”

How Much Time In The Sun To Get 4,000 IU

You can do your own due-diligence on this if you wish. There’s lots of info out there. I did find this particular resource interesting. It does seem to coincide similarly to other general data.

Interpreting the chart above…

20 minutes “sunbathing” may be approximately equivalent to about 4,000 IU of vitamin D. That’s obviously with a lot of exposed skin (and no sunscreen). After that initial exposure time, I would certainly apply sunscreen!

About 1 hour “jogging” in the sun equates to about 4,000 IU of vitamin D. I presume a ‘normal’ amount of exposed skin on the arms, legs, face. Probably wearing shorts.

I don’t get the 3 hour Golf equivalent… Unless they’re presuming long pants?

Adjust the times above to just one-third if the UV Index is about 12 (which is very high).

Adjust the times above by 3X if you’re elderly, obese, or dark skin.

When is the best time of day for vitamin D from the sun?

Midday is the best time, as the sun is at its highest point and your body may manufacture it most efficiently around that time of day.

“If your shadow is longer than your body height, you can’t make any vitamin D,” “Between 10 a.m. to 3 p.m. is the usual window for significant sun exposure,” [source: Holick]

Interesting factoid:

The amount of UVB radiation available depends on the angle at which the sun’s rays strike the earth. Because of the effect of the sun’s angle, even in completely clear skies, synthesis of vitamin D in the skin is impossible for four months of the year in Boston, Massachusetts (for example).

[ Read: My Daily Vitamin Supplements For Health and Well Being]

[ Read: Vitamin D Should Be The Public Health Message]

>> My D Supplement (5,000 IU)
(view on amzn)


  1. About 15 yrs. ago I had colon cancer. About 7-8 yrs. ago I read a medical paper suggesting that those who had colon cancer were also deficient in Vit. D. When I had the cancer I had an inside job so little exposure to the sun. I then began taking vit D. Since then I have read many reports on the many places in the body where Vit D is needed including reports about Vit. D & Covid. It doesn’t just stop rickets as we were previously told.

    1. i had colon cancer about 9 years ago, i think i might need to check into more vit D.

      1. Hubby had that kind. Was deficient in Vitamin D for years. Never made that cancer connection though. Just had started on vitamin d a few months prior to the diagnosis. Doc had noticed it on bloodwork and put him on it. Wow.

    2. I have been watching reports and the information is now that Vitamin D is much more than a simple vitamin, it is also a hormone. Was following one of the doc’s on u tube, and several reports are on it there…according to recent studies most are deficient, and 10-20 K could be taken safely for more than 2 years without toxicity…researchers who study immunity say an optimal level is 80 ..Many processes in the body depend on Vitamins we know little about ..including D3 and K2( the K vitamin that moves minerals. Iodine has also been implicated in same processes

  2. Age for sure. When I mow I use SPF. What is the balance between skin cancers and getting enough D when you are older. Supplement.

    1. Oil of Oregano i use on many skin blemishes.. has many qualities.. a hat that shades the face and neck will prevent excessive exposure and will not give disease from chemicals. The essential oils i can use but “the slathers”..nope not I

  3. If you have any auto-immune disease you should be having your vitamin D levels checked annually. I take 10k daily and fall only in the mid-range each year when tested. When I was below the norm I took 20k daily to get it up to mid-range. Now the 10k maintains! And, oddly enough we live in a state with 300+sunny days a year, and I am out in it daily! I do NOT use sun screen….I take a B50 every day, and I don’t burn (and am a RED HEAD….though silver now). Burned like nobody’s biz as a child….obviously vitamin B deficient.

  4. This is all very interesting! We live at aprox. 64 degrees North Lat. At best, our sun is rather low on the horizon. I thought I was all set with sun sourced Vit. D3 as, in summer we have 24 hours of light… True in winter not so much… but with the temps, you’re pretty much covered anyway & will be more inclined to also wear sunglasses due to the low angle of the sun.
    On a different note, I was thinking, we never heard of skin cancer 50 years ago and sun screen didn’t exist back then, at least I don’t recall it. So.. was pondering, could sun screen contribute to the rise in skin cancer? Of course not I reasoned. Then, I read that Vit. D3 fights cancer and… that sun screen blocks Vit. D3. Hmmm! Well anyway.

    1. Far North,
      I remember hearing years ago that sunscreen would stop the rays from tanning your skin, but that it actually helped cause cancer because of the ingredients in it. Doctors have said that burns cause cancer more than a tan, so there is such thing as a “healthy tan,” but it shouldn’t be that deep, deep tan that people get when they’re outside all of the time.

      I remember seeing a picture of an over-the-road trucker whose left side of his face was super wrinkled and had cancers, but his right side was “normal” and looked much younger. Too much sun can definitely be a bad thing!

      Personally, I wear sunscreen when I know I’ll be out in the sun for long hours at a time (beach, lake), since I don’t want a sunburn, but I don’t wear it for daily walks, mowing, etc.

  5. Approx 20-30 mins here in the UK sun April-Sept directly on skin I.e vest/shorts clothing gives me approx 10-12000 iu per day.

Comments are closed.