The Canine Ledger

"Finish the Course": Antibiotics for Dogs

"Always finish the course" isn't backed by evidence. What the dog guidelines say about course length, and why you still shouldn't stop early alone.

Written by thecanineledger

In 2017, a group of infection researchers wrote in the BMJ that “the idea that stopping antibiotic treatment early encourages antibiotic resistance is not supported by evidence, while taking antibiotics for longer than necessary increases the risk of resistance” (Llewelyn et al., BMJ 2017, opening section only). They were writing about people.

While that challenges one of the best-known rules in medicine, it doesn’t mean you should stop your dog’s antibiotics when it seems better. This page explains what the dog evidence says, why course lengths are getting shorter, and what to ask your vet.

1. Where “finish the course” came from

Public health campaigns. The BMJ authors quote a 2016 World Health Organization message telling patients to “always complete the full prescription, even if you feel better, because stopping treatment early promotes the growth of drug-resistant bacteria.”

The message has shifted. They note that US and English public health bodies “have replaced “complete the course” with messages advocating taking antibiotics “exactly as prescribed.””

The new wording matters for dogs too. “Exactly as prescribed” means the dose, the timing and the length your vet chose. It doesn’t mean stopping when you decide.

Our note: The BMJ article is about human medicine, and we read only its opening section because the rest is paywalled.

2. What the dog evidence says

There’s no general rule. We found no veterinary study that tests “finish the course” as a general rule. The evidence is different for each type of infection.

Bladder infections. A 2012 trial noted that “there are no studies in dogs to determine the appropriate duration of treatment for simple, uncomplicated UTIs”, which were then usually treated for 7 to 14 days (Westropp et al., Journal of Veterinary Internal Medicine 2012). UTI is urinary tract infection. The trial compared a 3-day course with a 14-day course in 68 dogs. Clinical cure rates were 88.6% and 87.9%.

But that trial has limits. The 3-day course used a different drug at a high dose. It doesn’t show that any antibiotic can be stopped after 3 days. The trial was funded by the manufacturer of the 3-day drug.

Skin infections. The 2025 guidelines on canine pyoderma (bacterial skin infection) from the International Society for Companion Animal Infectious Diseases (ISCAID) are clear: “There is no evidence to support extending systemic antimicrobial therapy beyond the resolution of clinical signs associated with infection” (Loeffler et al., Veterinary Dermatology 2025). Systemic means tablets or injections, not creams or shampoos.

Our note: We could read only the abstract of the same society’s 2019 urinary infection guidelines (Weese et al., The Veterinary Journal 2019, abstract). The full text is behind a paywall. The abstract doesn’t give a recommended course length, so we don’t either.

3. Why you still shouldn’t stop early on your own

Your vet decides when the infection has gone. For superficial skin infections, the guidelines say antibiotics can be stopped “when primary lesions of pyoderma (papules, pustules and erythematous epidermal collarettes) are no longer found.” That’s a clinical judgement, often with a skin test.

Rechecks are built in. The guidelines suggest an initial 2-week course for superficial infections, with a recheck “scheduled prior to the end of the course to determine whether systemic treatment can be stopped or whether longer treatment is required.” For deep infections the initial course is 3 weeks.

If a recheck isn’t possible, the guidelines say treatment “can be extended to avoid stopping treatment before veterinary assessment.”

Looking better isn’t the same as cured. The guidelines prefer skin treatments alone for surface skin infections, keeping tablets for dogs that don’t respond. In their review of trials of skin treatments alone, “Lesion improvement was noticeable in most dogs within 1–2 weeks, resolution within 3–4 weeks.”

Our note: We used skin infections as the main example because the 2025 guidelines are open access. Other infections may differ, so follow your vet’s advice for your dog’s infection.

4. What to ask your vet

  • How long should this course be, and why?
  • Should we book a recheck before the course ends?
  • What should I do if my dog seems better before then?
  • What should I do with leftover tablets?

Don’t save leftovers for next time. A different infection may need a different drug, or none.

If your dog gets worse on antibiotics, or develops a reaction such as facial swelling or difficulty breathing, call your vet now.

Our note: The advice on leftovers and reactions is ours, not the sources’. Ask your vet or pharmacist how to dispose of unused antibiotics.

→ Antibiotic-Resistant Skin Infections (MRSP) · → Does Diarrhoea Need Antibiotics? What the Evidence Says

5. What we could not verify

Commonly saidWhat we found
“Stopping early causes resistance”Not supported by evidence, in people. Longer courses increase resistance risk.
“Always finish the course, whatever happens”Out of date. The newer advice is “exactly as prescribed”, with your vet deciding the length.
“Longer is safer”No. For skin infections, there’s no evidence for continuing beyond resolution.
“Every dog UTI needs two weeks”Not necessarily. One trial found a 3-day course worked as well, with caveats.
“I can stop when my dog looks better”No. Ask your vet first. Improvement often comes before cure.

Sources

Always confirm with your vet before acting on anything on this page.