Mayo Clinic: "Vitamin D toxicity is rare in people who take supplements, researchers report." The evidence is clear that vitamin D toxicity is one of the rarest medical conditions and is typically due to intentional or inadvertent intake of extremely high doses," writes Dr. Hollick, a professor of medicine, physiology and biophysics at Boston University School of Medicine.
Oncologists and much of the rest of the western medical establishment actually thrives on the epidemic of cancer and nowhere can that be seen more clearly than its attitude toward the sun and its preference for the super high toxicity of chemo and radiation therapy as opposed to the low toxicity of vitamin D, iodine and even selenium (when it is administered in the right form).
One study on vitamin D used as high as 540,000 units for severe lung disease. High dose vitamin D administration in ventilated intensive care unit patients has also been studied using 50,000 IU vitamin D3 or 100,000 IU vitamin D3 daily for 5 consecutive days (total vitamin D3 dose = 250,000 IU or 500,000 IU, respectively) without an cause for alarm.
One company in the USA makes tablets that are 50,000 and recommended as high as four a day (200,000 units for four days) for at risk patients. Now because of the FDA oppression they will not make such recommendations.
Again from the Mayo Clinic: Vitamin D toxicity, characterized by hypercalcemia, hyperphosphatemia, and suppression of parathyroid hormone, is usually observed when intakes are excessively high, in the range of more than 50,000 to 1 million IU of vitamin D per day and are maintained long-term for several months to years. Meaning a cancer patient, who is desperately trying to reverse their spreading cancer, could safely take 500,000 units a day for first week, 400,000 units for second week, 300,000 units for third week and 50,000 units a day from there after without even touching the toxicity of any form of chemotherapy.
When using a full protocol the need for ultra high dosages of Vitamin D for long extended periods of time would be reduced because other substances with similarly low toxicities would also be used at very high dosages. Thus one can easily imagine safe intakes of 100,000 to 200,000 units a day for two to three weeks without need for reduction.
Chemo and radiation therapies toxicities are thousands of times higher than D3 supplements. In one case study, a woman had a level of 476 ng/ml (1,171 nmol/l) after taking a supplement that gave her 186,900 IU of vitamin D3 per day for two months. When thinking of using high dosages for cancer patients without risk we are using D3 for shorter periods of time, for one month and then cutting back severely the second month to assure little to no risk.
Taking one 50,000 IU capsule of Vitamin D3 every two weeks will result in 80% of adults bringing their blood levels to above 40 nanograms/ millliliter, an optimal level for good health. A 50,000 IU capsule is the equivalent of amount of vitamin D from sunbathing for 3 days in a sunny climate. The skin produces approximately 10,000 IU vitamin D in response to 20–30 minutes of full body summer sun exposure—50 times more than the US government’s recommendation of 200 IU per day.
 Short-term effects of high-dose oral vitamin D3 in critically ill vitamin D deficient patients: a randomized, double-blind, placebo-controlled pilot study. Critical Care volume 15 (2011)
 J Clin Transl Endocrinol. 2016 Jun; 4: 59–65. High dose vitamin D administration in ventilated intensive care unit patients: A pilot double blind randomized controlled trial