Hi Cathie,
We use injectable preparations orally - weekly if you're concerned, but not desparate; daily if the situation is pretty dire; monthly if your goal is maintenance or prevention.
Dose in all instances:
5000 IU per lb daily of vitamin A, to a max of 500 000 IU
750 IU per lb daily of vitamin D, to a max of 75000 IU per day
As the animal improves, scale back the dose frequency.
Continued use over years will cause a transient hypercalcemia tha resolves with cessation of the protocol. Short term risk of hypercalcemia is slim even with aggressive dosing.
Hope that helps,
Steve