In the past, possible Vitamin D Toxicity was cited as the reason not to supplement above 400 IU daily. More Recently in the UK, official sources cite 4,000 IU daily as the upper safe dose. In the USA official sources (the US Institute of Medicine) suggest no more than 10,000 IU daily will avoid risk of VDT……….

The three physician authors of this report have between them some 120 years of patient-facing experience. In that time, collectively, just one single case of Vitamin D toxicity was encountered - in a patient who had been taking 20,000 IU per day over many years.
Putting it into context, by comparison with severe vaccine side-effects, VDT occurrence is less than negligible.


It should be emphasised that, apart from individuals with rare clinical conditions, e.g. sarcoid or other granulomatous diseases; renal issues; etc., a daily supplementation level of 4,000 IU (or equivalent at weekly or monthly intervals) is perfectly safe, as are short-term higher daily doses, as discussed in the COVID-19 Exit Strategy Report, in order to achieve ‘Sufficiency’, then followed on by daily 4,000 IU.


Unfortunately, as indicated earlier, ‘officialdom’ presents an unhelpful, and unnecessary confusing picture. In the 2016 UK SACN (Scientific Advisory Committee on Nutrition) Report, ‘Vitamin D and Health’ a daily dose of 400 IU is recommended, with 1,000 IU as the upper limit. In the same report, ‘Europe’ is reported to have 4,000 IU as its upper limit; and the US Institute of Medicine is reported to state “based on the available data it unlikely that symptoms of toxicity would be observed at daily vitamin D intakes below 250 µg/(10,000 IU)”. More recently, the NHS website advises “Do not take more than 100 micrograms (4,000 units) of vitamin D a day as it could be harmful.”


Having said that, a recent, major retrospective study investigating over 20,000 blood tests for the occurrence of VDT found only one case, illustrating how extremely rarely it occurs: Vitamin D Toxicity–A Clinical Perspective.  Front. Endocrinol., Sept. 2018


A relevant extract from this report is given below:
In statements released over the last decade, the Institute of Medicine (IOM) (15) and the Endocrine Society (14) have both concluded that acute VDT is extremely rare in the literature, that serum 25(OH)D concentrations must exceed 150 ng/ml (375 nmol/l), and that other factors, such as calcium intake, may affect the risk of developing hypercalcemia and VDT. Regardless of additional risk factors for VDT, many studies provided evidence that vitamin D is probably one of the least toxic fat-soluble vitamins, much less toxic than vitamin A (4). Dudenkov et al. (2) researched more than 20,000 serum 25(OH)D measurements performed at the Mayo Clinic from 2002 to 2011 to determine the prevalence of VDT, demonstrated by the presence of hypercalcemia. The number of individuals with a serum 25(OH)D concentration >50 ng/ml (>75 nmol/l) had increased by 20 times during that period. However, relatively high 25(OH)D concentrations coincided with a normal serum calcium concentration. Only one patient, with a25(OH)D concentration of 364 ng/ml (910 nmol/l), was diagnosed with hypercalcemia. Pietras et al. (16) reported that healthy adults in a clinical setting, receiving 50,000 IU of vitamin D2 once every 2 weeks (equivalent to approximately 3,300 IU/day) for up to 6 years, maintained 25(OH)D concentrations of 40–60 ng/ml (100–150 nmol/l) without any evidence of VDT. Those findings were consistent with the observation by Ekwaru et al. (17) that Canadian adults who ingested up to 20,000 IU of vitamin D3per day had a significant increase of 25(OH)D concentrations, up to 60 ng/ml (150 nmol/l), but without any evidence of toxicity.