My PCP and endocrinologist also think that people are overdoing vitamin D. (Similar to when people overdid vitamins E and A in the past, which was a problem with oil-based vitamins. We can 'pee away' vitamin C and a lot of the water-solubles but some of the oil-solubles build up in the system.) I take vitamin D3 and keep it under 1500 IU per day and it's balanced with algae-derived calcium, K2, magnesium, etc. And annual blood work includes testing D level.