Recently, I came across a BMJ (“British Medical Journal”) article entitled “Vitamin D 
intoxication and severe hypercalcemia complicating nutritional supplements misuse” It was a single case report whereby a middle-aged man supplemented 150,000 IU (!) Vitamin D on a daily basis. This was ingested on top of another very high-dose multi-nutrient cocktail including Vitamin K2, Vitamin C, some B vitamins and also Omega-3s. You can read the details here.
Some of the symptoms of excess Vitamin D are
- Vomiting, diarrhea and nausea
- Leg cramps
- Appetite loss but excessive thirst
- Fatigue, dizziness and headaches
- Other neurological symptoms such as tinnitus
Why are adequate levels of Vitamin D so important?
Vitamin D has made a lot of headlines in the context of anti-viral treatment in the past 2.5 years, and a lot of effort has been put into finding adequate doses, ranges and also limitations of Vitamin D supplementation. In 2021, for instance, Trinity College in Dublin published an article called “Further Evidence that Vitamin D might protect against severe Covid-19 disease and death“, which reiterated the importance of this vitamin (oh well, I prefer to consider it a hormone, actually).
Why this is the case and what the mechanisms are can be read here. This is a blog post I wrote a good while ago, but it still has some very relevant information concerning Vitamin D. It covers the sources of Vitamin D, how you can make sure you know when your skin can manufacture it and other practical tips. I didn’t go into any details regarding optimal doses and ranges, so let’s catch up with this here!
Do I have to supplement?
Whether you have to supplement or not depends on many factors, some of which are:
- Your skin type
- Genetic variants in metabolism of vitamin D and also receptor sites
- Your geographic location
- Diet choices
- Your level of insulin resistance (this is a new insight for many people!)
In short- without regular testing, it is a guessing game whether you have your optimal levels or not. But- supplementing 150,000 IU (the current RDA is 400 IU, which is on the opposite extreme, in my opinion) without super close medical supervision and, by the sounds of it, on a daily basis, is certainly a very bad idea. This would never be recommended by a registered health practitioner! There are cases where high doses are administered by a GP but this is for very specific purposes.
The best times for testing are around February (when levels in most people living in the Northern hemisphere decline and people tend to become more vulnerable to infection) and then usually also in October, if you manage to expose yourself regularly to sunshine (in a safe way) during the summer months. If you live in the Southern hemisphere, this is obviously the exact opposite!
Fortunately, home testing kits have become much more affordable and widespread. In the UK, I like the NHS test and otherwise, there are lots of other options such as OmegaQuant. Most companies that offer testing will also give you guidelines for supplementation depending on your test results, but I’d still recommend getting in touch with a well-experienced healthcare practitioner to give you advice if you have any doubts.
What are optimal levels?
Based on various studies and reviews, a tentative approach to optimal levels of 25-hydroxy-vitamin D is as follows:
- Vitamin D sufficiency: 40-50ng/mL (100-125 nmol/L)
- Optimal physiologic range: 50-90 ng/mL (125-225 nmol/L)
Then there’s the supraphysiologic and pharmacologic dosing for specific conditions, which has to be done under strict supervision. Prior to Vitamin D3 supplementation, it’s reasonable to assess renal function. It is important to watch out for adequate magnesium intake during supplementation and ideally to combine supplements with vitamin K2.
What’s the practical approach?
As with everything in health (and life), balance is important. If you’re outdoors a lot and expose your skin in a safe way to the sun during the summer months, you might get away without supplementation during the winter (because D is a fat-storable vitamin). However, in my experience, most people who live in climates where the sun is not always guaranteed, even in the summer months, benefit from Vitamin D at around 4,000 IU daily according to the NHS.
