I always give them a shot. Then I know which chicken I medicated. If separate them from all our chickens then I will put medicine in the water. I give them 1cc of penicillen with 1/2cc of tylan 50 under skin on breast. I draw up penicillin then draw up 1/2cc of tylan. I put little extra air in syringe and mix med back and forth so mixed. Tylan can be hard on tissue and I don't have many problems with it doing that. If separated I give 3cc of tylan injectable added to 1 gallon of water for them to drink also. If only shots I give them every other day for minimum of 3 shots to get them well. Usually sick ones don't lay so I don't worry too much about eggs but I would not eat anything from the bird for at least a week or two. This almost always get them well