Some studies have shown that in patients with documented vitamin D deficiency, a very high, cumulative dose of at least 600,000 IU administered over several weeks appears to be necessary to replenish stores within the body. This goes to show that having a blood test to detect your exact vitamin D levels can be beneficial in telling you exactly how to replenish your body levels properly. Ideally, you want to supplement with a high-quality, whole food-based multivitamin or vitamin D supplement until your blood level of vitamin D is between 50–60 nanogram per milliliter.
Rodents are somewhat more susceptible to high doses than other species, and cholecalciferol has been used in poison bait for the control of these pests. It has been claimed that the compound is less toxic to non-target species. However, in practice it has been found that use of cholecalciferol in rodenticides represents a significant hazard to other animals, such as dogs and cats. "Cholecalciferol produces hypercalcemia, which results in systemic calcification of soft tissue, leading to renal failure, cardiac abnormalities, hypertension, CNS depression, and GI upset. Signs generally develop within 18-36 hr of ingestion and can include depression, anorexia, polyuria, and polydipsia." 
A United States Institute of Medicine report states: "Outcomes related to cancer , cardiovascular disease and hypertension , and diabetes and metabolic syndrome, falls and physical performance, immune functioning and autoimmune disorders , infections, neuropsychological functioning, and preeclampsia could not be linked reliably with calcium or vitamin D intake and were often conflicting."  : 5 Some researchers claim the IOM was too definitive in its recommendations and made a mathematical mistake when calculating the blood level of vitamin D associated with bone health.  Members of the IOM panel maintain that they used a "standard procedure for dietary recommendations" and that the report is solidly based on the data. Research on vitamin D supplements, including large-scale clinical trials, is continuing.