Bioavailability of oral hydromorphone(dilaudid) is not very high, somewhere around 35%. Intranasal is a bit higher at about 52%. IV hydromorphone is the most efficient ROA, with almost all of the dose being absorbed. I dont necessarily recommend shooting prescription pills, however.
Tolerance develops very rapidly with hydromorphone because it is very short acting. 4 mg of Dilaudid orally is a fairly low dose to someone who is somewhat opiate tolerant, especially if they have been taking hydromorphone.
Those bio percentages can vary drastically from person to person, they are just somewhat of an average.