I should have used the word "daily" for clarity. The daily upper limit is 4000 IU/day, as per
Ross AC, Taylor CL, Yaktine AL Del Valle HB (2011). Dietary Reference Intakes for Calcium and Vitamin D. Washington, D.C: National Academies Press. p. 435. ISBN 0-309-16394-3.So that is well below the 10,000-20,000 IU I said was toxic.
10.000 IU is indeed not an acutely toxic dose. Taking doses in the same order of magnitude (40,000 IU/day instead of my 10,000 to 20,000) orally has proven to be toxic after a few months.
If we take my upper quote for "toxicity", 20,000 IU, that's half of the dose that was found toxic in the studies. So my statement is correct, only not as an acute, but a chronic (daily) dose.
A US government website says that oral vit. D doses > 10,000 IU/day are toxic, vindicating my statement (except you are right that I should have used the word "daily"):
https://http://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/Long-term intakes above the UL increase the risk of adverse health effects [1] (Table 4). Most reports suggest a toxicity threshold for vitamin D of 10,000 to 40,000 IU/day and serum 25(OH)D levels of 500–600 nmol/L (200–240 ng/mL). While symptoms of toxicity are unlikely at daily intakes below 10,000 IU/day, the FNB pointed to emerging science from national survey data, observational studies, and clinical trials suggesting that even lower vitamin D intakes and serum 25(OH)D levels might have adverse health effects over time. The FNB concluded that serum 25(OH)D levels above approximately 125–150 nmol/L (50–60 ng/mL) should be avoided, as even lower serum levels (approximately 75–120 nmol/L or 30–48 ng/mL) are associated with increases in all-cause mortality, greater risk of cancer at some sites like the pancreas, greater risk of cardiovascular events, and more falls and fractures among the elderly. The FNB committee cited research which found that vitamin D intakes of 5,000 IU/day achieved serum 25(OH)D concentrations between 100–150 nmol/L (40–60 ng/mL), but no greater. Applying an uncertainty factor of 20% to this intake value gave a UL of 4,000 IU which the FNB applied to children aged 9 and older, with corresponding lower amounts for younger children.
Excessive sun exposure does not result in vitamin D toxicity because the sustained heat on the skin is thought to photodegrade previtamin D3 and vitamin D3 as it is formed [6]. In addition, thermal activation of previtamin D3 in the skin gives rise to various non-vitamin D forms that limit formation of vitamin D3 itself. Some vitamin D3 is also converted to nonactive forms [1]. Intakes of vitamin D from food that are high enough to cause toxicity are very unlikely. Toxicity is much more likely to occur from high intakes of dietary supplements containing vitamin D.