Kidney disease in dogs: stages, signs, and knowing when it is time
A clinically reviewed guide to canine kidney disease: IRIS staging, the signs to watch for, what treatment can and cannot do, and how to know when it is time.
If you are reading this, your dog has probably either just been diagnosed with kidney disease, or you have noticed something that is making you wonder. Drinking more. Losing weight. A vet using a phrase like "CKD" or "kidney failure" or "renal values are up". The shock of those words is real, and the internet rarely makes it clearer.
This article is written to give you a calm, clinically accurate picture of what kidney disease in dogs actually is, how vets in the UK think about its severity, what the practical signs look like at each stage, what treatment can and cannot do, and the question most families eventually have to ask: how do I know when it is time?
The two presentations of kidney disease
Kidney disease in dogs comes in two main shapes. They look similar from the outside but behave very differently underneath.
Acute kidney injury (AKI) is a sudden loss of kidney function, often over hours or days. It is usually triggered by something specific: a toxin (lily pollen, raisins, grapes, antifreeze, certain medications), a severe infection, a urinary blockage, or a drop in blood supply during illness or anaesthesia. AKI is a medical emergency, but it is also the form of kidney disease where, with prompt hospital care, full recovery is possible. The kidneys can repair if the cause is remedied quickly, depending on the degree of damage already sustained.
Chronic kidney disease (CKD) is the slow, progressive version. It develops over months or years as nephrons, the tiny filtering units in the kidneys, are gradually lost. By the time a dog shows clinical signs, around two thirds of the working kidney tissue is already gone. CKD cannot be reversed. It can, however, very often be managed for a long and comfortable time, and that is what most of this article is about.
If you have an older dog, particularly an older Labrador, Cocker Spaniel, or any small-breed senior, CKD is what your vet is almost always referring to. AKI is the emergency situation that presents itself very rapidly; CKD is the long, gentle decline that arrives with age.
How UK vets stage kidney disease: the IRIS system
When your vet mentions a "stage", they are talking about the framework set by the International Renal Interest Society, known as IRIS. IRIS staging is the system used across the UK and most of the world to grade how far CKD has progressed. It is built around two blood test markers and a urine result, looked at in combination when the dog is stable and well hydrated.
The two blood values that matter most are creatinine and SDMA (symmetric dimethylarginine). Both SDMA and creatinine levels increase when the kidney starts to function less effectively. SDMA is a more sensitive indicator of damage than creatinine and will rise earlier to reflect this. Vets also look at urine concentration (specific gravity), urine protein loss (UPC ratio), and blood pressure, because all three independently affect how the kidneys will fare from here.
The four IRIS stages are, in plain terms:
- Stage 1. Kidney damage is present but creatinine is still within the normal range. SDMA may be raised. The dog usually looks well at home. This stage is often picked up on a routine senior blood panel rather than because anyone noticed a problem.
- Stage 2. Creatinine is mildly raised (roughly 125 to 250 µmol/L). Many dogs are still drinking and eating normally, though some families notice slightly increased thirst or a thinner coat. Diet changes start to make a real difference here.
- Stage 3. Creatinine is moderately raised (roughly 250 to 440 µmol/L). Clinical signs are usually obvious now: increased thirst and urination, weight loss, reduced appetite, intermittent vomiting, lethargy. Most dogs in this stage need active management, not just monitoring.
- Stage 4. Creatinine is markedly raised (above 440 µmol/L). The kidneys are failing to keep up. Dogs are typically unwell: poor appetite, nausea, sometimes mouth ulcers, weight loss, weakness. Treatment in this stage focuses on comfort more than on slowing the disease.
Signs to watch for at home
Kidney disease announces itself slowly, and the early signs are easy to put down to "just getting older". Knowing what to look for, and at roughly which stage to expect it, helps you have the right conversation with your vet at the right time.
The two signs most families notice first are increased thirst (polydipsia) and increased urination (polyuria). Bowls drain faster. The dog asks to go out more often, particularly through the night. This is typically the body trying to compensate for kidneys that can no longer concentrate urine properly. It often appears in stage 2.
As the disease progresses into stage 3, you tend to see weight loss despite a reasonable appetite, then appetite changes: pickiness, walking away from a half-finished bowl, taking longer to eat. Intermittent vomiting, often in the morning before food, is common at this point, as is a sense that the dog is quieter or less interested in walks. Coat condition may dull.
In stage 4, signs become harder to miss and more directly tied to comfort. Persistent nausea. Mouth ulcers that you can sometimes see on the gums or tongue, and a distinctive ammonia-like smell on the breath caused by waste products that the kidneys can no longer clear. Marked weakness, occasional disorientation, and dehydration that does not resolve with drinking. Some dogs become reluctant to eat at all.
None of these signs in isolation proves kidney disease, and most can be caused by other conditions in older dogs. What matters is the pattern over time: more drinking alongside weight loss and demeanour change. That pattern, taken to your vet, is what gets a blood test and a stage.
What treatment can and cannot do
CKD cannot be cured, but it can very often be managed. Treatment has two goals: slow the loss of kidney function where possible, and keep the dog feeling well for as long as possible.
In the earlier stages (1 and 2), management is mostly built around diet. Prescription renal diets are lower in phosphate and have carefully balanced protein, and the evidence that they extend comfortable life in CKD dogs is some of the strongest we have in small-animal medicine. Omega-3 fatty acids are also recommended. Your vet may also start a phosphate binder if blood phosphate is rising, and blood pressure medication (typically an ACE inhibitor or telmisartan) if hypertension or significant urine protein loss is found. Hydration is very important: free access to fresh water, always.
In stage 3, the same tools are used more actively, often alongside anti-nausea medication (maropitant, mirtazapine for appetite), appetite support, and sometimes subcutaneous fluids given at home a few times a week. Many dogs feel meaningfully better once nausea is controlled, and families often describe getting "the old dog back" for a while. This is the point in time when active multi-modal care makes the biggest difference to quality of life.
In stage 4, the focus shifts. Active treatment continues if it is helping, but the question becomes less "how do we slow this" and more "how do we keep them comfortable". Fluids, anti-nausea, pain relief if needed, gentle feeding of whatever the dog will eat. We do not promise outcomes at this stage. We watch the dog, day by day, and let how they are feeling lead the conversation.
When is it time?
This is the question that brings most families to articles like this one, and it deserves a straight answer. The honest answer is that there is no blood value that tells you it is time. The decision is led by quality of life, not by a number on a report.
A useful starting point for decision making is five questions, asked gently, about the last week of your dog's life as you have actually observed it:
1. Appetite. Are they eating something most days, with a bit of interest, or are meals becoming a struggle? 2. Mobility. Can they still get up, move around, get to the water bowl and the garden without distress? 3. Comfort. Are they free from persistent nausea, pain, or breathlessness, most of the time? 4. Pleasure. Are there still things they look forward to: a particular person coming in, a corner of the sofa, a short sniff in the garden? 5. Dignity. Are they still able to be themselves: continent, clean, settled, recognisably the dog you know?
If the answer to most of these is "yes, on most days", you are usually still in management territory. If the answer to most of them is "no, and it is not improving", and that pattern has held for more than a week despite treatment, the conversation is no longer about slowing the disease. It is about how to say goodbye well.
This is a decision that almost always feels too early until, in hindsight, it feels too late. Both feelings are normal and neither means you got it wrong.
How we can help
We are a vet-led at-home euthanasia service. When the time comes, our visiting vets come to your home, take time to explain everything, and use sedation first so your dog is calm and unaware before the final injection. There is no rush. Most visits last around an hour, paced by what your family needs.
If you would like to talk through where your dog is, we are happy to do that without any commitment to booking. We work across the UK.
A final note
Living with a dog who has kidney disease is a long act of love. The decisions are real, the days can feel heavy with responsibility, and the right moment is rarely obvious until you are standing in it. Whatever stage you are in, you are not alone. If you would like to talk it through, our team is on the phone any day, including evenings and weekends. There is no script and no pressure, only time to listen.
Reviewed by Dr Rebecca Goodwin, BVetMed CertAVP(EM) MRCVS, on 12 May 2026.
Sources
- International Renal Interest Society (IRIS), staging guidelines for CKD in dogs and cats: https://www.iris-kidney.com/
- British Small Animal Veterinary Association (BSAVA), Manual of Canine and Feline Nephrology and Urology, current edition.
- Royal College of Veterinary Surgeons (RCVS), Code of Professional Conduct, guidance on euthanasia and end-of-life care.
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