General medical information should be on-topic, such as:
What are the advantages/disadvantages of these three different treatments commonly used for $disease?
How often do indoor-only pets contract FIV?
$professional_publication had information about a promising new treatment for $condition a year ago; what further work has been done?
We suspect food allergies; what alternatives are there to the expensive prescription diet?
What is the general prognosis for $diagnosis?
Information like that is already available online (e.g. through VIN), and we also hope to attract veterinary professionals who may have questions of this sort.
On the other hand, questions seeking personal medical advice should be off-topic, such as:
Should I subject my elderly pet to surgery for $problem?
Should I vaccinate my indoor pet for FIV?
If I accidentally skip a dose of $medicine should I just skip it or double up the next one?
(Many personal details here, ending with) what should I do?
Taking a cue from other sites that can attract professional-advice questions, we should develop some disclaimer language for the "about" page and help center. See, for example, Mi Yodeya, which does not give professional rabbinic advice.