Fatal underdose

Since vitamin D has been the topic of a fair amount of media coverage, I've received many questions about this fascinating "nutrient." A day doesn't go by without several nurses, friends, even fellow physicians stopping me to ask about vitamin D.

When I inform them that the average dose for females in this region (upper Midwest) is 4000-5000 units per day, 5000-6000 units per day for males, they are all surprised. "Then why did they say just take your multivitamin every day, or just drink your milk on the news?"

Many people are even more surprised, sometimes completely turned off, when they hear that, to be truly confident of adequate vitamin D dosing, a blood level of 25(OH) vitamin D3 needs to be checked. Now we're talking real hassle!

But there is no other way to do it. In order to obtain the full potential benefits of vitamin D, such as reduction in blood sugar and sensitization to insulin, reduction in cancer risk (especially prostate, colon, and breast), reductions in blood pressure, increased bone density, not to mention markedly increasing the likelihood of stopping or reducing your heart scan score, then achieving a desirable blood level of 25(OH) vitamin D is necessary.

Checking a blood level of vitamin D is no more difficult than having a cholesterol test, unless, of course, your doctor balks at the idea. (Time for a new doctor if that occurs.)

All too often, someone will be convinced they are taking a sufficient dose of vitamin D of, say 2000 units per day, only to discover that their blood level of 25(OH) vitamin D is something like 17 ng/ml--severe deficiency, sufficient to leave them exposed to all the undesirable consequences of vitamin D deficiency. Even though 2000 units per day represents 500% of the Institute of Medicine's recommended Adequate Intake for adults, to those familiar with the Track Your Plaque program it likely sounds like a child's dose.

Many variables enter into the equation in your body that determines your need for vitamin D: body size (heavier or larger people need more, with obese people often requiring enormous doses); sex (men need more than women); age (aging results in dramatic loss of ability to activate vitamin D in the skin); race; skin color (darker skinned people require more). Trying to guess your need is a fool's game. It's also a game that can seriously compromise your health and your hopes of ever stopping or reducing your heart scan score.

The message is clear: You cannot guess what your vitamin D need is. You cannot properly judge your vitamin D requirement by your age, body size, sex, or any other characteristic. Having a tan or a lack of a tan is a lousy indicator, as well. A simple blood level of 25(OH) vitamin D is an absolute necessity to gauge your vitamin D status, both before starting and while on your supplement.

Members of Track Your Plaque: Watch for the 30-some page booklet, The Track Your Plaque Complete Handbook on Vitamin D and Heart Health, which will be released in the next day or two.

Copyright 2008 William Davis, MD

Comments (8) -

  • Anne

    4/27/2008 10:00:00 AM |

    I'm asking my doctor for this blood test for my vitamin D levels on Thursday and I'm taking along a print out of this blog plus a previous blog you wrote called 'Vitamin D toxicity' (6th Feb). I hope my doctor will do the test - I live in the UK where you can't change your doctor like you can in the US. Fingers crossed my doctor will be reasonable. I currently take 4,000iu D3.


  • Darcy Elliott

    4/27/2008 4:21:00 PM |

    Great to hear this Dr. Davis! Hopefully they'll be shipping in bulk across the country and "Coming soon to a Cardiologist Near You"
    Darcy Elliott

  • Anne

    4/27/2008 9:26:00 PM |

    I was one of those whose vitamin D level fell from 46ng/ml to 26ng/ml while on 2000 IU of oil based D3/day. This decline occured during the winter probably due to the fact that I was not getting exposed to sunlight as I had been during the summer.

    When I asked my PCP to check my winter D level, he told me it was not necessary as I tested high at the end of summer. He was quite surprised when I brought in a lab report of 26 (I have a new PCP now). Apparently I need much more oral vitamin D in the winter - that makes sense.

    How often do we need to test?

    Looking forward to reading your Vitamin D Handbook.

  • Anonymous

    4/28/2008 2:04:00 PM |

    Enjoyed reading the vitamin D handbook last night.  It is full of good information and well worth the read.    

    Thought to mention a curiosity noticed by a barber living in Florida.  My parents spend the winter in Florida, in the summer they live in the mid-west.  A few weeks back the two of them had a hair cut.  While chatting their hairstylist mentioned - ever since she moved to Florida she has found that Floridians hair grow quicker.

    Florida is known as the "Sunshine      State"  Maybe vitamin d plays a part in hair growth too.

  • John Doe

    4/28/2008 3:43:00 PM |

    I was very surprised to know that my Vit D level was at 2.865, with the normal range being 7-75 ng/dL.

    How bad is that ? I am 26 years old.

  • Anonymous

    4/28/2008 3:46:00 PM |

    I was very surprised to know that my Vit D level was 2.876 ng/dL, with the normal range being 7-75 ng/dL.

    I am a 29 year old Indian, living in New Delhi, which gets a lot of sunshine and have never taken Vitamin D supplements.

    What daily dosage would you recommend ?

  • Linda

    5/8/2008 11:31:00 PM |

    It is very important to see a doctor to get information on your vitamin D levels. Especially living in the NorthWest! No sun! Haha Smile I recommend after seeing a doctor, start taking supplements to get vitamin D also. You can find more info on vitamin D supplements here.

  • Jessica

    5/19/2008 6:19:00 PM |

    My doctor says "Taking vitamin D supplements without checking your 25-OH level is like baking a cake without knowing the temperature of the oven."

    I'll always remember that!

    Have you since release the Vitamin D and heart health handbook you referred to in this post?

    I'd like to get a copy of that.