Because of my enthusiastic promotion for optimizing Vitamin D (hereafter referred to as “D”) in my patients, I am often asked “ how much is too much; can it be harmful?” Therefore, in order to be fair and balanced, let’s look at the potential for D toxicity, so-called Hypervitaminosis D. After all, D is a fat soluble vitamin, meaning it can build up in the tissues and may not be released quickly like the water soluble ones — C and B vitamins for instance.

The main downside of too much D is high blood calcium levels. This causes a myriad of symptoms: nausea & vomiting, constipation/ or diarrhea, poor appetite, excessive thirst & frequent urination, as well as bone pain in the early stages. With progression the latter stages of D toxicity can lead to muscle weakness, fatigue, confusion and even death. This progression typically takes weeks to months, especially in an otherwise healthy person. However, with blood calcium levels so routinely available, this should never happen. If blood calcium is chronically elevated, kidney stones could develop, especially in susceptible people with pre-existing kidney problems and/or endocrine (glandular) problems and/or liver problems. So don’t take chances. Ask your doctor to help in your quest for optimum D! Especially if you are in this class of people.


D3 is the naturally occurring form of D synthesized in the skin from sun exposure and also occurring in fish oil and other natural products. Thus I will only consider this ideal form of supplementation. I will not cover the prescription 50,000 iu form, but only OTC doses.

For normal adults 2,000 iu daily is recommended by The Endocrine Society and is certainly safe. The Vitamin D Council recommends 5,000 iu daily, which I also consider very safe for most people and probably ideal for elderly, dark skinned people and those over 200 lbs. Even 10,000 iu daily for short term use (one month or less at a time) is safe and a good idea if fighting an acute illness, such as sinusitis, bronchitis, flu/cold or any other type of infection or stressor. Never use more than 10,000 iu daily unless instructed by your doctor.


To know for sure that you are getting optimum D, check a simple blood level—readily available (although some insurance companies refuse them as unnecessary—always ask for cost info). The ideal target is 70ng/ml. This is the highest level one can achieve by staying in the summer sun all the time. My references are: 0—29=Deficient, 30—49=Sufficient, 50—100=OPTIMUM, 101—149=Taking Too Much D, 150+=Potentially Toxic—see above. If symptoms exist or calcium level is elevated, see a doctor immediately.


Almost everything we do in medicine has a Risk/Benefit Ratio. I feel strongly that the benefits to taking more than the RDA (400 iu) of D far outweigh the risks for healthy adults. I start people on 2,000 iu daily and tell them to ask their primary care provider to check a D level at their next routine visit (make sure you have been consistently taking it for at least 3 months). I find most people need between 2,000—6,000 iu daily to get close to the ideal blood level of 70 ng/ml. (Make sure your lab reads in these units. If they read results in mmol/l, divide by 2.5 to convert to ng/ml.)

There are just so many health benefits available to optimizing D that I feel this is now the single most important actionable health project. Why not start today? Cognition is better—some even believe Alzheimer’s can be prevented or delayed by D supplementation. Every organ works better—most importantly the cancer surveillance systems of the body—with hundreds of studies showing less overall cancer risk when D is optimized. (Some feel the evidence on cancer risk reduction is not strong enough to claim this yet—I disagree. ) I have many skin cancer patients who have turned around their escalating numbers of skin cancer surgeries on optimum D—after being on it 1—2 years.

Once Again Praying His Benefits For YOU and YOURS!!!

Steven A. Smith, MD, FACP
Psalms 103


If you are pediatric age, have kidney problems, are pregnant or nursing, or have glandular problems (endocrine), consult with your doctor prior to optimizing your Vitamin D3 intake. Be aware that most, but not all, practicing doctors follow practices similar to the above. If your doctor does not recommend Vitamin D3, get a second or even a third opinion.