My 93-year-old uncle has had two heart surgeries this year, a stent and a valve replacement. When the valve failed, he was severely dehydrated. He has recovered nicely except that he has some lab values that are slightly out of range. I have tried to get his vitamin D level checked twice, and both times the doctor couldn't figure out how to get it paid through Medicare. Even if I had his level, I am now concerned about the fact that it might not be safe for me to supplement vitamin D. There is a urologist who comes to his town occasionally but don't know if he is vitamin D savy.My question is whether I cans safely supplement with D3 in the face of diminished kidney function? His urea nitrogen is 24 mg/dL (18 is the upper end of the reference range at the lab). His creatinine is 1.20 (1.00 is the upper end). His glomerular filtration rate is 56.44 (needs to be above 60). He is also slightly anemic. The kidney foundations say that someone with kidney disease should not supplement D3 without a prescription). I don't want to take a chance on endangering him, and the doctors are ignorant of the need for D3 to be in the normal range for anything other than osteoporosis.Of course, I could check the 25(OH) level regularly, but I have no idea if the phosphorous and calcium would be normal.