I myself would have written,
She has acute kidney failure and her blood tests have turned out to be very bad.
as I understood you, Lizrj, to mean that the blood tests were taken when acute kidney failure was suspected, but your sentence is grammatically correct.
Yes, we were taught at school that "good" "bad" "perfect" were absolute conditions and that no-one could be very, good, exceedingly bad, or nearly perfect. However, very few people use these words in that way.
Do any of you not say, "His cold was very bad", or "The weather was really very good for the wedding" or other things like this?