Most cat antibiotic courses run 7 to 14 days, but the number is not a habit and it is not the same for every infection. Length comes from 3 things: what tissue is infected, whether a culture was taken, and what the recheck shows. The drug, the dose, and the interval are the vet's call and belong on a prescription label, never on a guess from the internet. What an owner controls is finishing the course and showing up for 2 rechecks.
Three infection groups, three lengths
Group 1, urinary tract infection. An uncomplicated bladder infection in a cat with no stones and no kidney disease is often treated for 7 to 14 days, and shorter courses of 3 to 5 days are used in some cases only when the vet has a culture result and the cat improves fast. Group 2, skin and wound infection, including bite abscesses: 7 to 14 days, and a drained abscess often needs 10 to 14 because the pocket fills with dead tissue. Group 3, upper respiratory and dental infection: 7 to 10 days, extended to 14 when there is nasal discharge that has lasted more than 10 days or a tooth root involved.
Why the last 3 days matter more than the first
Fever drops in 24 to 48 hours and the cat starts eating again at day 2 or 3, which is exactly when owners stop. At that point the bacterial load is down by roughly 90 to 99 percent, and the surviving 1 to 10 percent are the cells that were least sensitive to the drug. Stopping at day 3 of a 10 day course leaves a partially treated population, and the relapse that follows is often resistant to the same drug. Finish the labeled days unless the vet says otherwise in writing.
| Infection group | Typical course | Early recheck | End recheck | What is checked |
|---|---|---|---|---|
| Bladder, first episode | 7 to 14 days | 48 to 72 hours | 7 to 14 days after the last dose | Urine culture, straining, urine volume |
| Bladder, recurrent | 14 days | 48 to 72 hours | 7 days after the last dose | Culture plus sensitivity, stone check |
| Skin or bite abscess | 7 to 14 days | 48 hours | 3 to 5 days after drain removal | Pocket size, discharge, appetite |
| Upper respiratory | 7 to 10 days | 72 hours | 10 to 14 days | Nasal discharge, breathing rate, hydration |
| Dental or post-extraction | 7 to 10 days | 48 hours | 10 to 14 days | Gum color, mouth odor, chewing side |
Recheck 1: 48 to 72 hours in
This is the check that catches the wrong drug. If the fever is still there at 72 hours, or the cat is eating less than half its normal ration, the plan needs to change: a culture, a different class, or a search for an abscess that was never drained. Do not wait for the end of the course to report a cat that is getting worse, and do not top up the dose yourself to compensate.
Recheck 2: 7 to 14 days after the last dose
The cat looks normal and the course is finished, so this visit feels optional. It is the one that finds relapse. For bladder cases the standard is a urine culture 7 to 14 days after the last dose, because sediment alone misses low-grade infection. For wounds it is a look at the pocket and a weight check. Cats lose weight quietly during a course: a 5 percent drop on a 4 kg cat is 200 g, and that is a reason to recheck sooner. Trend tracking is set out in the weight trend chart.
Prescription only, and why that is not bureaucracy
Dose scales with weight and with kidney and liver function, and the same tablet that suits a 5 kg cat can be 3 times too much for a 2 kg kitten. Human antibiotics come in strengths made for 70 kg adults, and some are toxic to cats at any dose. Leftover tablets from a previous course are the worst option: the drug may be wrong for this tissue, expired, or stored warm for 12 months. Give what is on the label, at the labeled interval, for the labeled number of days. If the label is missing or unreadable, call the clinic rather than reconstruct it.
Missed doses and thrown-up pills
Late by 2 hours: give it and shift the rest of the schedule. Late by more than half the interval: give the next dose at the normal time and do not double up. A pill vomited within 30 minutes counts as not given; after 2 hours, assume it was absorbed and wait. Log every miss on the fridge note, because 3 or more missed doses in a 10 day course is a reason for the vet to extend it rather than pretend it did not happen.
Side effects worth a phone call
Soft stool is common in the first 3 to 4 days and usually settles; diarrhea that lasts past 48 hours, vomiting more than 2 times in a day, or a cat that stops eating needs a call. Antibiotics disturb the gut population, and a probiotic given 2 hours apart from the dose is a common way to soften that. Never add a second antibiotic, a human anti-diarrheal, or a supplement without asking, and keep the cat's water intake normal. A cat that also ate something questionable needs that checked in parallel, which is what the toxic item list is for.
Red flags that outrank the schedule
Breathing faster than 40 per minute at rest, a belly that is hard to touch, no urine for 12 hours, yellow gums, or a cat that cannot stand: go now, and bring the prescription label. A cat that has finished a full course and is still febrile at day 14 needs imaging or a culture, not a third round of the same tablets. Vaccination status can matter during recovery, and antibody questions belong with titer testing rather than guesswork.
Steps for the next course
- Ask 3 questions at pickup: how many days, what recheck date, what counts as not improving.
- Write both recheck dates on the calendar before you leave the clinic.
- Give every dose at the labeled interval and log misses.
- At 48 to 72 hours, score appetite, fever, and the local sign.
- Book the 7 to 14 day end recheck even if the cat looks perfect.
Frequently asked
Can I stop antibiotics when the cat seems fine?
No. Fever usually drops in 24 to 48 hours and appetite returns by day 2 or 3, but at that point roughly 1 to 10 percent of the bacteria are still alive, and they are the least sensitive ones. Stopping a 10 day course at day 3 leaves a partially treated population, and the relapse that follows often resists the same drug.
How soon should a cat be rechecked after a course ends?
For a bladder infection, a urine culture 7 to 14 days after the last dose; sediment alone misses low-grade infection. For a wound, a look at the pocket 3 to 5 days after the drain comes out, plus a weight check, since a 5 percent loss on a 4 kg cat is 200 g and worth acting on.
Why can't I use leftover antibiotics from a previous illness?
Because the drug may target the wrong tissue, may be expired, or may have sat warm for 12 months. Dose scales with weight and with kidney and liver function, and human tablets are made for 70 kg adults, with some toxic to cats at any dose. Only the prescribing vet can match drug, dose, and interval to this cat.