Vitamin D toxicity

It is the craziest thing.

The notion of vitamin D being easily and readily toxic has grabbed hold of many people, including my colleagues who were taught that vitamin D was toxic in medical school based on the skimpiest (and often misinterpreted) observations in a handful of unusual cases.

In my practice and in the Track Your Plaque program, we routinely use doses of 2000-10,000 units per day, occasionally more. We are guided by blood levels of 25(OH) vitamin D3. I have personally never witnessed vitamin D toxicity.

Here's an interesting graph from Dr. Reinhold Vieth. Those of you familiar with the vitamin D argument know that Dr. Vieth is among the few genuine gurus in the vitamin D world.

From Vieth R. Vitamin D supplementation, 25-hydroxyvitamin D concentrations, and safety. Am J Clin Nutr 1999;69:842-856. (Full text is available without charge.)

In the graph, the X's represent toxicity; circles fall within the non-toxic range. (Toxicity is generally defined as a level sufficient to raise blood calcium levels, "hypercalcemia.") Note that the 25(OH) vitamin D3 levels are given in nmol/L; to convert to ng/ml units that are customary in the U.S., divide the nmol/L value by a factor of 2.5.

You will notice that toxicity is virtually unheard of until the dose exceeds 10,000 units per day. Beyond 10,000 units per day, the curve heads upward sharply and toxicity does become a possibility, though not an absolute (since there are circles above 10,000 units).

You may also notice that the curve is relatively flat from vitamin D doses between 200 units and 10,000 units (log scale on x axis; arithmetic scale on y), the range of most common doses for vitamin D supplementation.

Another perspective on vitamin D blood levels is to examine the blood levels of people who are young and obtain plentiful sun exposure. Lifeguards, for instance, have blood levels of 84 ng/ml (210 nmol/L) without ill-effect. (Sun exposure cannot generate vitamin D toxicity, because of a feedback safety mechanism in skin.) While this may not represent an ideal level since they represent an extreme, it does provide reassurance that such levels are non-toxic. I also point out these levels occur in the youthful since most people lose 75% or more of vitamin D activating capacity in the skin by their 70s. Most of us over 40 are kidding ourselves if we think that a suntan provides sufficient vitamin D.

Keep in mind that it is not necessarily the dose of vitamin D that is toxic, but the blood level it generates. I take 10,000 units of vitamin D as a gelcap per day to maintain my blood level between 50-60 ng/ml (125-150 nmol/L). This strategy helps me keep my HDL in the 70-80 mg/dl range, my blood sugar around 90 mg/dl, my blood pressure <120/80, and I no longer experience colds nor winter "blues."

Copyright 2008 William Davis, MD

Comments (26) -

  • mike V

    2/6/2008 5:19:00 PM |

    Dr D:
    I take up to 4000 IU per day depending on season and have recently had a zero CTA scan, so I personally have high confidence in vitamin D3.
    From time to time I see references to the possibility that excessive D can produce soft tissue/arterial calcification in some people. I understand of course that Vitamin K2 menaquinone is an essential partner in proper calcium homeostasis.
    Are you completely without concern at the blood levels discussed?, or should people with marginal kidney performance or other moderate metabolic conditions be cautious?
    Would appreciate your thoughts.

  • mtflight

    2/6/2008 5:31:00 PM |

    Where does one get 10,000 IU caps?

    I take 4000 IU capsules from Carlson Labs (called "Solar Gems")--the oil in the caps is fish oil, so that's a plus, and my multivitamin has 1,000 IUs.

    P.S. Thanks for the blog, I'm a big fan!

  • Dr. Davis

    2/6/2008 9:33:00 PM |

    There are clearly groups of people who should work with their doctor when it comes to vitamin D, particularly people with kidney disease or dysfunction; history of kidney stones; glandular diseases like hyperparathyroidism; a history of high calcium.

  • MrSardonicus

    2/6/2008 9:58:00 PM |

    If taking 4,000 IU of Vitamin D a day increases one's HDL by a relatively small number -- say, 10 -- but it's still low, what do you think is the likelihood hiking the amount will further increase HDL?

    Also, do you take calcium with your Vitamin D?

  • Dr. Davis

    2/6/2008 10:01:00 PM |

    I have never seen 10,000 capsules. I'm hoping somebody comes out with such a preparation. I wasn't aware of the 4000 unit capsules. Thanks for the tip!

  • Dr. Davis

    2/6/2008 10:04:00 PM |

    I would not advise taking more vit D just to raise HDL.

    Blood level of vit D is the parameter to assess vit D adequacy. I would regard a rise in HDL as a fortuitous side phenomenon.

  • Brandon

    2/6/2008 11:00:00 PM |

    “…and I no longer experience colds nor winter "blues."

    Careful, this sort of personal testimonial lends to sounding more like a “nutritional guru” instead of medical professional examining scientific evidence.

    I’m not saying you’re incorrect, it may be your experience and it may be absolutely true, but a stick to the clinical facts. You’re talents are better suited to being a “medical watchdog” than a “dietary duck.”

  • Anonymous

    2/7/2008 12:19:00 AM |

    Dear Dr. Davis,
    I would love your opinion of my doctor's protocol regarding my recent diagnosis of osteopenia in my hips (t-scores -1.1 and -1.2 femoral neck, my spine was normal, -0.2).  I'm a 56 year old woman, 115 pounds, just went through menopause, taking Zocor and Lotrel (high cholesterol and hypertension both run in my family), I exercise regularly.  My doctor said he wanted to see how well I absorb Vit D, so he ordered a blood test, however, he ordered the D1,25 test (results 35 pg/mL), NOT D25 which I understand is a truer biomarker.  He prescribed Vitamin D, Calcitriol, one 0.025 capsule per day for one month, with no restrictions on my Calcium/Vit D intake through supplements, after which he said to return for another Vitamind D blood test (another D1,25).  I've read that Calcitriol can cause hypercalcemia.  I've also read that D1,25 will not tell you how well you're absorbing Vitamin D.  Based on that, I felt I was wasting my time and risking hypercalcemia, so I stopped taking the Calcitriol.  Should I tell my doctor that he ordered the wrong blood test?  Also, which prescription Vit D should I be taking? I have no other health issues.  Thank you, Dr. Davis.

  • Dr. Davis

    2/7/2008 12:58:00 AM |

    Thank you, but I disagree.

    I add my experiences to that of probably over 1000 patients in the last two years who have shared similar effects.

  • Dr. Davis

    2/7/2008 1:00:00 AM |

    Hi, Ruthie-

    Lots of issues. However, it sounds like your doctor is simply toeing the conventional line of prescription drugs. It may be time to either prod your doctor to get up to date on vitamin D, or to find a doctor willing to engage in the discussion.

  • Anonymous

    2/7/2008 1:27:00 AM |

    Do you know if any one is making or developing an at home vitamin D3 testing product?

  • Dr. Davis

    2/7/2008 2:55:00 AM |

    Wouldn't that be wonderful?!

    Unfortunately, I do not know of any such commercially available product. However, it would be a tremendous boon to this movement of self-empowerment in health care that I see coming for the future.

  • Anonymous

    2/7/2008 5:36:00 AM |

    I am taking vitamin D3 two softgels of 2000 IU each daily, one in the morning and one in the evening. I want to know if I get the same effect if I take two softgels together instead of taking one twice a day. Thanks.

  • Anne

    2/7/2008 9:12:00 AM |

    Hi Ruthie,

    I'm 54 and diagnosed with osteoporosis (T scores -3.7 in hips and -3.1 lumbar spine). I've been prescribed calcium supplements (as well as Strontium Ranelate) but I've found that I'm very intolerant to the calcium, no matter whether I try calcium citrate, calcium carbonate or calcium amino acid chelate, so since Christmas I've stopped all calcium supplements and upped my vitamin D3 intake to 4000iu per day (not prescription, I wish it was then it wouldn't be so expensive...vitamin D costs a lot in the UK, much more than the US) so that I absorb my dietary calcium as well as possible. I feel very confident that this will work, especially in view of a previous blog from Dr Davis about calcium:

    Plus logic tells me that it is not lack of calcium that causes osteoporosis but other factors. People in third world countries such as Africa on suboptimal diets have very low levels of dietary calcium but they don't usually get osteoporosis...they get more sunshine (vitamin D) and do much more physical work. I'm doing plenty of weight resistance exercise now !


  • Dr. Davis

    2/7/2008 1:03:00 PM |

    Yes, no difference.

  • moblogs

    2/7/2008 2:25:00 PM | supply D3 in 1k, 5k and 50k capsules, and with delivery rates that are reasonable for those out of the US.
    I've been taking 5k for the past 2 weeks and don't feel bad on it, but will be getting blood levels checked within a season to see if I'm personally responding correctly.
    The 400IU average was just based on preventing rickets.

  • hoosierville

    2/7/2008 7:03:00 PM |

    Dr. Davis,
    I've had great results from increasing my vitamin D intake with regards to my lung capacity. I'm a recovering smoker with moderate copd and, after being hospitalized for pneumonia, am finally recovering to a point where I can almost run up and down steps. I attribute this to my "D" supplements which I began taking about a month ago. I can take deep breaths for the first time in years.

    My question is about the supplements themselves. I see very expensive D3 tablets and then I see the regular vitamin D. Is one better than the other? Is there a great deal of difference? Thanks.

  • jabs28

    2/8/2008 6:05:00 PM |

    I am surprised to see how many people are gettingtheir their Vitamin D requirements with supplements.  Go out into the sun WITHOUT sunscreen for 10-15 minutes a day and then supplement the rest.  Remember it also takes about 40 glasses of milk to equal 4000 iu's of Vitamin D.  You can get that from about 15 minutes of sun exposure depending on your age and ethnicity.  The more melanin in your skin, the longer you need to expose it.

  • Anonymous

    2/8/2008 6:10:00 PM |

    The capsules I take (the Solar Gems) are 6 cents a 4000 IU softgel:

  • hoosierville

    2/9/2008 2:25:00 PM |

    I live in Indiana. It's going to be 6 degrees out in just a few minutes. We haven't seen the sun in weeks. What do you suggest, tanning beds? I'll do it but not until I hear that they're safe. Be reasonable, not everyone lives where they can get natural sunlight. I think that's part of the Vitamin D deficiency problem.

  • TedHutchinson

    2/10/2008 9:08:00 PM |

    I have been taking the same 5000iu Biotech capsules Moblogs uses.
    I was 147.5nmol - 59ng when tested at the end of summer (UK latitude 53) although I did not take a D3 on days when I knew I would be able to get near full body sun exposure at midday.

    As others have reported, I also have not had a cold or flu over the winter (so far and still touching wood) others I am regularly in contact with have been unlucky.
    (I also did not need to get my SADLIGHT down from the attic this winter)

  • MattWheeler

    2/11/2008 3:26:00 AM |

    Something in the my 7 month TYP program (6000iu D3 gelcap, Slo-Niacin 1.5g, 3g+ fishoil, low wheat-suger) has really helped with joint pain I have had for 8 years.  This has allowed me to lift weights 3 times per week and thus reduced my bodyfat from 27 to 19 percent.  I look and feel much better.  I am 51, male at 215 lbs.

  • Anonymous

    2/11/2008 10:00:00 PM |

    Oh, is it because I take vitamin D3 that even with people dropping like flies around me (with colds, flu, etc) I never get sick? I have always thought it surprising that I tend not to get these things, given that I do have a number of autoimmune conditions. I have only ever used tablets (1000IU 1/day) and my vitamin D3 (250H) level is 52ng/mL.

    However, my vitamin D2 (250H) level is <4ng/mL and my vitamin D (1,25) level is only 24pg/mL (normal range 22-67). Should I (and is it possible to?) do anything to increase those levels?

  • Anonymous

    12/3/2008 2:51:00 PM |

    * * D2 v. D3 * *

    * * D2 vs. lupus vulgaris * *
    ("administered in alcoholic solution is key" to success of therapy)

  • George Mclaughlin

    10/9/2010 12:37:54 AM |

    Very interesting article. I find myself concerned about the side effects of vitamin D supplements, as opposed to sunlight-derived vitamin D.

    I'd love to hear your thoughts on this article, which appears to be quite well cited:

  • buy jeans

    11/2/2010 8:39:57 PM |

    In my practice and in the Track Your Plaque program, we routinely use doses of 2000-10,000 units per day, occasionally more. We are guided by blood levels of 25(OH) vitamin D3. I have personally never witnessed vitamin D toxicity.