Being a vet is a pretty demanding job. It's worse when you're not feeling good. And it's really difficult to get a day off.
I've been sick off and on for the last six weeks. It started as a cold around Christmas that turned into bronchitis. As I got over that I developed a different virus, this time affecting my sinuses. I've been taking high doses of vitamin C and have been trying to get rest and drink lots of fluids. What I've really needed was to have several days off where I'm not doing anything and simply taking it easy. Unfortunately, that's easier said than done.
The veterinarian isn't the only important person in a practice. I couldn't work effectively if not for my techs and receptionists. However, if one of them calls in sick we can usually call another person in or find some way to pick up the duties among the people there that day. The day goes on and we continue to see patients normally. But if I or one of my associates calls in sick we can't easily find a last-minute replacement. If we're down a tech or receptionist it's stressful and reduces our efficiency. If a vet calls out we can't see patients. If we're not seeing patients then sick pets are going untreated as well as our business takes a small hit to the bottom line.
This means that most vets come in to work unless they have one foot in the grave. I'll only call out if I'm having profuse vomiting or running a fever. In just about every other circumstance I'm pushing through the illness and loading myself up on cold medicine in order to make it through the day. I also try to avoid direct contact with clients (such as shaking hands) in order to minimize the spread of my illness.
There are many days when I and the other doctors in my practice continue to work when we'd tell one of our staff to go home. I hate this reality, but it doesn't change the fact that it's not easy for us to simply decide that we're sick and want to stay in bed. In fact, I think I've done that one time in 18 years in practice.
So if you go to your vet and they are less energetic than normal or are moving and thinking slower than you're used to seeing, be patient with them. They are probably working while sick and doing the best that they can to keep your pets healthy.