Some people have much lower response to the same vitamin D dose.

There can be as much as 4X less response in the blood level to the same vitamin D dose.

Here are some of the reasons for a low response - both known and possible

1. The vitamin D was not taken with the evening meal or largest meal of the day or perhaps not in the evening
2. There was little fat in the meal taken with vitamin D
3. The fat taken with the vitamin D was not primarily mono-saturated
4. The person did not have enough of the co-factor Calcium –bio-availability of Vitamin D
   (be careful – must also not have too much Calcium = not more than 500 mg unless pregnant or nursing)
5. The person did not have enough of the co-factor Magnesium – bio-availability of Vitamin D
6. The person did not have enough of the co-factor Boron – bio-availability of Vitamin D
7. The person was older – guts of seniors do not get nutrients as well
8. The person was overweight – a lot of vitamin D goes into fat, rather than the blood reference to high BMI
9.   Gut bacteria not deal with vitamin D properly - possible
10. The person had a medical condition which was consuming vitamin D – MS, HIV, etc.
11. The person had absorption problems in their gut
12.   Bloodstream not properly transport the inactive vitamin D to the liver/fat- possible
13. The person had poor liver function to store the vitamin D
14. The person had poor kidney function or poor endocrine function – to make the active form
15. The person had previously taken Vitamin D2
16. The person was consuming cola or was smoking – both of which use up vitamin D
17. The person has different genes   not only the genes which accept active vitamin D in the blood the final stage,
    but also genes in the gut, liver, and kidney which affects the response of the blood to a vitamin D dose
    Inuit genes – gut evolved for low vitamin D adsorption
18. Blood does not transport the active form in the blood normally = Vitamin D Binding Protein problem
19. Cells does not properly react to the active vitamin D = poor function of the Vitamin D Receptor = VDR

Other possible reasons include

1. Excess Vitamin A (unsure if Vitamin D just only blocks vitamin D from acting)
2. The person is taking Accutane or excessive Vitamin A or cod liver oil – which are vitamin D antagonists
   note: not sure if this reduces vitamin D in the blood or just blocks the benefits of vitamin D
3. Low state of health
4. High stress - Cortisol uses up Cholesterol, which is also needed to produce vitamin D
   note: this may not be involved in the creation of vitamin D from supplements
5. Different form of vitamin D3 – some of the solid forms appear to be only 1/3 as effective
6. Products may have < 1/3 the amount stated on the label
7. Taking drugs such as Statins, Antiseizure, Prednisone, AIDS drugs, Orlistat, Questran, Dilatin, Phenobarbital, and Rifampin,

Dr. Grimes shows about a 2X difference in response to vitamin D by individuals from the same initial level

Blue bar show vitamin D level (ng) the person had initially
Pink bar next to it shows vitamin D level (ng) after 20,000 IU weekly of vitamin D3
CLICK HERE for more about Dr. Grimes in the UK
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See also VitaminDWiki

• How you might double the benefit of your vitamin D
  Many of which are mentioned above
• No – 10 minutes per day of sun-UVB is NOT enough
• Many reasons why vitamin D deficiency has become epidemic in past 30-40 years
• web page which was copied to make this blog post