It's a good idea to try to vary the injection site. Just "south" of the shoulder blades is where it's safest, and most comfortable for the cat. You can do it in the center of this area, but must always be extremely careful to stay away from the spine. A little to the left or right of the center is fine too - the skin is usually loose enough to insert the needle comfortably. Unless you are giving a large amount of fluid (over 200mL) you want to avoid multiple needle sticks. My Mickey was getting 200mL and was fine with one injection site. The fluid will settle in different areas depending on the cat. I wouldn't suggest more than 2 injections per hydration session.
Sub q's are administered according to each individual cat's requirements. The frequency and amount of fluids will vary depending on the severity of the CRF. Some cats are fine for years with twice weekly administration, others require daily fluids, some even twice daily. I have never heard of a vet suggest just once weekly simply for the convenience of the owner. It would be like giving a med whenever the owner could get around to it. Likes meds, hydration is effective only if you stick to the prescribed schedule. It takes commitment - the cat's health depends on it.
Hmmm, interesting. I think there are many people here who do it alone. It's helpful, however, to have an IV pole, or some place to hang the bag above the cat. We (I should say my DH), always just used our dining room chandelier to hang the bag from...worked like a charm!
My vet even recommends it for placid ones... She will Not give fluids alone to a cat...
