VITAMIN D DOSING:   The optimal blood level of vitamin D level [vitamin D 25-OH] is probably ~70 ng/ml- -according to my conservative internist as well as my decade long study of the subject. Lab slips say normal is 30-80 or 30-100 ng/ml and that  >100 ng/ml is toxic, alarming everyone.  Levels up  to 200 ng/ml are safe, at least in the short run.  It is not advisable to keep the level above 100.  Especially above 150 ng/ml, there is an increased cardiovascular disease over time. 

The half-life of 6 weeks allows once a month dosing — convenient, easier to remember, and much cheaper.  In my experience with 100’s of patients, compliance is vastly better if dose is once a month instead of weekly or daily.

A  loading dose is advisable.  Even when giving the  appropriate dose, it may take six months to reach a steady state—because of the long half-life.   The loading dose can be up to 600,000 I.U. in an adult (reference below; 12 pills of 50K—I have given this amount to patients in my office dozens of times).

At minimum, give double the daily dose for the first month.   Six 6 months is  a long time to wait for benefit.

Over a decade ago, I asked a Chassidic Rabbi [Hershel Meisels, founder of a diabetes organization, and health commentator on Kol Mevaser] what the daily dose of D3  should be for children.  He said 1000 I.U. for every 25 lbs. I began to read on the subject. He was right. 1 000 I.U. per 25 lbs is true for adults as well.

Monthly doses for children: [you will give up if you try to give daily D3 to 3 children].

A 10-pound infant needs 400 I.U. per day or 12,000 I.U. once a month.  If using drops with  4000 I.U. per drop,  the infant’s dose would be  3 drops once a month.

A 50 lb child needs 15 drops/month.

A 100-pound child needs 4000 I.U.’s per day, which is one drop per day, and 30 drops once a month. All doses can be extrapolated from this.  A 10 pound baby is 1/10 the size, so three drops per month is correct. A 25-pound child would be ¼ of  30 = 7-8 drops per month

Use capsules of 50,000 I.U.’s for adults [from the Internet]of D3 is by far the cheapest and easiest way.  #120 capsules of the  50K I.U. from Zahler’s is ~$20. At 3 capsules per month, this will last 3.3 years or  <$7 per year.   Daily capsules of  5000 I.U.’s cost triple that.  The savings adds up for several people in a family.

A 125 lb person needs 5000 I.U. /day = 3 capsules monthly of 50,000 I.U.

175 lbs needs 4/month.  200 lbs need 5/month;  250 lbs needs 10k/day = 6/month of 50K; you do not have to be exact.  But it is probably better to be a little too high then to be too low.

It is hard to become toxic. [I had one 105-pound woman who managed to do it.  She took 50K I.U. per day for 150 days. She became quite confused from hypercalcemia, was hospitalized for a couple of days, and completely recovered]. Toxicity occurs if one takes ≥ 10 X  of appropriate dose for a few months.  All reported toxicity in adults has been at ≥ 50 K I.U. per day or more, usually more. They were usually on it four months before becoming symptomatic. Some people can take 50 K I.U. daily indefinitely, because they can metabolize it rapidly.

People over 75 y.o. sometimes only need 1000-2000 I.U./day because of slower metabolism. Check the level.


There is a reason some people have a dark skin.  Melanin blocks UV light and prevents skin cancers, so people exposed to a lot of UV light evolved dark skins.  The health of  humans who moved out of Africa and into Europe was less than optimal.  Because they could not make an adequate amount of vitamin D,  they quickly evolved  skin with much less melanin.  Swedes are whiter than Italians because they must make D quickly and abundantly to store for the winter.  Spaniards and Southern Italians can afford to tan easily and be swarthy, in order to avoid a lot of nasty sun-related skin cancers [melanomas are only partially sun-related].

Humans, always exposed to sunlight,  made  adequate amounts of this hormone for millions of years.  Being cultivators of crops for the last 10K-12K years is a tiny blink in the history of humans.  What covering from the sun did hunter gatherers wear?  There was no wool, no cotton, much less spinning wheels.  Fur and  material woven from plants were available, neither of which were comfortable in summer.  They surely wore something—to cover the genitals or something decorative.  Like the hunter gatherers who survive, the clothing was probably minimal in warm weather.

On any area of the skin, humans can only make vitamin D for a limited time.  No more can be made until the next day.   A pale skinned person sunbathing for one hour, when the sun is high,  can make up to 15,000 I.U.’s of D3 per day–day after day. When a suntan develops [to prevent skin cancers], it will take longer.   My guess is hunter gathers in temperate areas made on the high end of 5-15K/day of D3.

Skin color is an indication of how far one’s ancestors were from the equator.  Dark skinned people may need three hours to make the same amount, being from an area where the sun is high all year. The efficiency of manufacturing D3 varies widely with melanin, latitude, weather, air density (e.g., altitude), and inclination of the sun above the horizon.

MISCELLANEOUS INFORMATION ON DOSE AND HISTORY OF D3—a steroid hormone mistakenly named a “vitamin” in ~1922 by McCallum at Columbia.

Avoid vitamin D2  It is made from plants, available  by prescription  in 50,000 I.U. gel capsules, and intended to be taken once a week. It was grandfathered in as a prescription.  It was the only good source of vitamin D 80+ years ago. It  is less potent and has a shorter ½ life then D3. Until recently it was sometimes put in multivitamins.

Fortunately the vitamin D one buys without a prescription is now only D3—our own vitamin D.  

It is obtained from the lanolin of sheep. D3 is fat soluble, and is dissolved in lanolin.  When this oil reaches the end of the wool, the sun converts pre-D3 (7-dehydrocholesterol) into D3. When an ewe licks the wool of her boyfriend, or of her lamb, she obtains her dose of D3.

To make wool usable, the Australians press out the lanolin— about 300 ml from each sheep.

Lanolin is then sold to two factories in China, one in Germany, and maybe one in India. In a complicated process, pre-D3 is extracted and converted to D3. This business is critical and largely unknown.  It works like a clock.    Food animals  are  now raised in factory-like conditions with no sunlight.    If their feed were not supplemented with D3, these animals would be quite unhealthy.

A few of these factories may still make D2 from sea algae.  They have been reducing  D2 production,  fearing they might accidentally send D2 to companies providing feed for chickens, resulting in millions of dollars in losses.  Unlike humans, chickens cannot use D2 at all.

Only D3 fits into Vitamin D binding protein (DBP) of chickens.  The large amount of D3 stored in DBP contributes to the six-week half-life. DBP is almost identical in chickens and humans.  Two indications of the importance of D are:   #1: how necessary it is for  animal health, and #2: humans and chickens have preserved the same carrier protein since a common sauropsid  ancestor over  315 million years ago.

  • This is lifelong hormone replacement. The 3rd of 5 steps in the manufacture of this steroid hormone involves UVB striking the skin and converting 7-dehydrocholesterol into D3 (cholecalciferol).   No one in the developed world is in the sun enough to produce enough D3.
  • Vit D reduces risk of ≥ 20  cancers.  It also reduces risk of metastases.   A Vitamin D 25-OH level of 47 ng/ml is associated with a 50% lower risk of breast cancer (Anticancer Research 9/2011).  There is reason to believe higher levels reduce breast and colon cancer risk ~70%.
  • NOTE:   Prominently published in the New England Journal of Medicine, a large five-year Boston study [Manson, NEJM, 1/3/19]  set the cause of vitamin D back years.   The question was whether  vitamin D  prevented  cardiovascular disease and cancer.   I read the plan of the study 2012 and was       The negative outcome was predictable, if not inevitable.   A daily dose of Vitamin D3 2000 I.U.’s [50 mcg / 0.050 mg] is appropriate for a 50-pound child, not an adult.   The vitamin D 25-OH levels at the end of the study were 40 ng/ml  in the study group and 30 ng/ml in the controls, not a large difference.  One needs 30 ng/ml for good bones.  The benefits for cancer, diabetes, et al, seems to occur after around 50ng/ml.
  • Other studies indicate much higher levels are better. A study in Finland used 2000 I.U.’s  per day during the entire first year of life!—5 times the requirement of a 10 lb baby.   The incidence of subsequent type I diabetes plummeted 78%.   Later it was realized that 2000 I.U.’s per day in newborns was excessive, though no apparent harm was done.
  • Toxicity only occurs when taking ≥ 10 times the optimal dose for a few months.   All reported toxicity [usually industrial accidents] was at 50K I.U. /day, and usually did occur for several months.