Kidney Disease in Dogs and Cats: The Later Stages

If your veterinarian has told you that your pet’s kidneys are failing, you may have been living with the diagnosis for months or even years already. Kidney disease often moves slowly, and many cats and dogs do well on treatment for a long time. This article is about the later stages: what they usually look like, what can help your pet feel better, the signs that things are getting harder, and what families tend to weigh as they think about the decision ahead.

Kidney disease is one of the most common conditions in older pets, especially cats. Expert guidelines estimate that it may affect 30 to 40 percent or more of cats over 10 years old¹, and in a large study of cats seen by veterinarians in England, it was the most common recorded cause of death in cats aged five and older². Dogs get it less often, and once a dog is diagnosed, the time ahead is more often months than years³. Whether it’s your cat or your dog, you’re far from alone in this.

This article is part of our guide to common end-of-life conditions, and it’s meant to sit alongside your regular veterinarian, who knows your pet best and is the right person for questions about their treatment. Here, we want to help you understand what’s happening and what may lie ahead, and that starts with what “kidney failure” actually means, because the words can be confusing.

Your pet’s kidneys filter waste out of the blood and help keep the right amount of water in the body. When they’re damaged, waste products build up in the blood, and that buildup is a big part of what makes a pet with kidney disease feel sick.

Veterinarians usually call the long-term condition chronic kidney disease. It develops slowly and doesn’t reverse, though treatment can often slow it down and help a pet feel better. “Kidney failure” is the term most people use for its later stages.

To track how far it has gone, most veterinarians describe chronic kidney disease in four stages, using a system from the International Renal Interest Society (IRIS) that’s based mostly on blood tests⁴. Stages 3 and 4 are the later stages. In Stage 3, many pets start to show signs of being unwell, though how much varies a lot. Stage 4 brings a growing risk of illness throughout the body and of sudden, severe flare-ups called uremic crises⁴. The stage tells you roughly how much kidney function is left. It isn’t a countdown, and two pets in the same stage can feel very different.

Sudden kidney damage is a different illness. Acute kidney injury comes on over a short time and is an emergency, and it needs different care from the slow, chronic kind this article is about. Even so, if a pet with chronic kidney disease suddenly gets much worse, please call your regular veterinarian or an emergency clinic. With that in mind, here’s what the later stages of chronic kidney disease usually look like.

Kidney disease looks a little different in every pet, and cats in particular are good at hiding illness. As the disease advances, though, a handful of changes tend to show up, and most of them trace back to the same few problems: waste building up in the blood, the body struggling to hold on to water, and the strain all of that puts on the rest of the body.

The waste that builds up in the blood makes many pets feel nauseous, so they eat less, vomit, or stop eating¹. In dogs, the signs most often recorded alongside kidney disease include vomiting, a smaller appetite, bad breath and weight loss³. A cat who used to meet you at the food bowl may now walk away from it, and a dog who never skipped a meal may start leaving food behind.

Eating less shows up on the scale in time, though weight loss often starts long before a diagnosis. In one study of more than 500 cats, the cats were already losing weight three years before they were diagnosed, and the loss sped up afterward⁵. In dogs, muscle can tell you more than weight. A dog may still look a healthy size while losing muscle along the spine, hips and head, and in one study of dogs with kidney disease, severe muscle loss went with a much higher risk of dying⁶. So it’s the speeding up, and the muscle you can feel under your hand, that matter more than any single number on the scale.

Holding on to water is the kidneys’ other big job, and failing kidneys can’t do it well, so the body loses more water in urine. In dogs, drinking and peeing more, and leaking urine, are among the signs most often recorded with kidney disease³, and many cats show the same thirst. Even while drinking more, a pet can end up dehydrated, which adds to how tired and unwell they feel.

The litter box can show another change in cats: constipation. In one survey, 42 percent of cats with kidney disease passed stool less than once a day, compared with 15 percent of healthy cats⁷. Low potassium, which is common in kidney disease, can add to it¹, so it’s one more thing worth keeping an eye on.

All of this takes a toll on a pet’s energy. Many pets in the later stages are tired, sleep much more and seem weak, and several things add up here. Anemia, a shortage of red blood cells, is common in cats with kidney disease and tends to come on as it worsens, because failing kidneys make less of the hormone that tells the body to make red blood cells⁸. It can leave a pet tired and weak, with pale gums, and it’s something your veterinarian can check. Low potassium can also cause weakness and low energy¹.

Put together with muscle loss, these can show up as weak or wobbly back legs, in cats and dogs alike. In older cats, arthritis often comes along with kidney disease too⁹, so a cat who no longer jumps up to the windowsill may be dealing with both.

Some changes shouldn’t wait for the next checkup. Kidney disease is a common cause of high blood pressure in both cats and dogs, and high blood pressure can cause sudden blindness¹⁰. If your pet suddenly seems unable to see, bumping into furniture or missing the step they always take, please call your veterinarian right away. All of this raises a question nearly every family asks sooner or later: are they in pain?

The honest answer is that kidney failure seems to make pets feel sick more than sore. No study we’ve found has measured pain from kidney disease itself in cats or dogs. What the research does show is that the buildup of waste makes pets nauseous and takes away their appetite¹, and that tiredness and weakness come along with it. In one study, cats with kidney disease scored lower than healthy cats on comfort, energy and emotional wellbeing, and constipation, a poor appetite and anemia each went with lower scores¹¹. Some pets also develop a sore mouth, which can make eating harder still.

That isn’t the same as saying it’s painless. Feeling nauseous, weak and run down day after day is hard on a pet, and older pets with kidney disease often have painful conditions too, like arthritis⁹. The hopeful part is that some of what makes them feel worse, like nausea, constipation and anemia, is worth raising with your regular veterinarian, who may be able to help¹¹. Our article on recognizing pain in cats and dogs covers the signs that a pet is hurting.

The other question that often comes up is how much time is left.

There’s no way to know exactly, and every pet is different. Studies of pets with kidney disease do give a rough idea, as long as you remember that half the pets in a study lived longer than the typical (median) time it reports, and some lived much longer.

For cats, the picture is often measured in years in the earlier stages and in months in the last one. In one study of 211 cats, half of those diagnosed in Stage 3 lived longer than about two years, and half of those diagnosed in Stage 4 lived longer than about three months. In Stage 4, the range ran from a single day to more than five years¹².

The studies in dogs are smaller, and their numbers are shorter. In one, half of the dogs in Stage 4 lived longer than about two months¹³. In another, from a university hospital that saw sicker dogs, it was under two weeks¹⁴. Both used the dog stages from before IRIS updated them in 2026, so they don’t line up exactly with today’s stages.

In both cats and dogs, the same things tend to go with less time: a pet who has stopped eating, and heavy weight and muscle loss^5,​6. In one study of dogs, those who had stopped eating entirely lived a median of about a month, compared with about eight months for dogs who were still eating, if less than before¹⁴.

These numbers come from hospital records, and your pet may do better or worse. Our article on understanding survival times and life expectancy explains how to read numbers like these. Whatever the time turns out to be, there’s a lot you can do to help your pet feel better through it.

In the later stages, even the kidney specialists’ guidelines put comfort first: by Stage 4, treatments that help a pet feel better matter more than treatments meant to slow the disease¹⁵. Our article on keeping your pet comfortable at home covers eating, drinking, bedding and keeping clean for any sick or aging pet, so here we’ll focus on what’s specific to kidney disease.

Because failing kidneys let water slip away, many pets in the later stages need extra fluids¹⁵. Your regular veterinarian may suggest giving fluids under the skin at home, a common part of kidney care, especially for cats¹.

The idea can sound daunting, but most families who try it manage. In a survey of more than 400 cat owners giving fluids at home, most said it was easy or okay, both for themselves and for their cat¹⁶. Those owners had a few tips worth passing on.

Things to consider:

• Ask for a demonstration – Have your veterinary team show you how, and ask for written instructions or a video to take home. In the survey, fewer than half of the owners were given anything beyond the conversation.
• Warm the fluids – Warming the fluids was the most common tip. Ask your veterinary team how warm is safe.
• Follow with a treat – More than half of the owners gave a treat afterward.
• Ask about the needle – The size of the needle and how long it took both affected how well cats tolerated fluids, so it’s worth asking about options.

Fluids and other daily treatments aren’t easy for every pet, though. In another study, cats with kidney disease scored especially low on the part of a quality of life tool that measures the burden of their care, like being medicated and taken to the vet¹⁷. If your pet struggles with fluids, pills or vet visits every day, that struggle is part of their quality of life too, and it’s worth raising with your regular veterinarian.

Eating can become its own daily struggle. In a large survey of cat owners, more than four in ten cats with kidney disease had an abnormal appetite, and about half of those ate poorly or needed coaxing most days of the week¹⁸. So if you find yourself coaxing your pet to eat, you’re in good company.

Medications can help with nausea, vomiting and a poor appetite¹⁵, but medical advice isn’t something you should get from the internet, so please ask your regular veterinarian what might help your pet. That’s also the time to ask about food: if your pet is on a kidney diet and is barely eating now, ask what matters most at this stage. In the meantime, our comfort care article has ideas for tempting a reluctant eater.

Beyond fluids and food, a few simple habits help you stay ahead of changes.

Things to consider:

• Keep water close – Fresh water should always be within easy reach¹⁵. Our comfort care article has more ideas for helping pets drink.
• Watch the litter box – Constipation is common in cats with kidney disease⁷ and goes with feeling worse¹¹, so tell your veterinarian if your cat is passing stool less often or straining. For dogs, keep an eye on accidents and on how much they pee.
• Weigh them every week or two – Weight loss tends to speed up as the disease advances⁵, and a scale shows the trend. A cat can be weighed on a baby scale, or by weighing yourself holding them and then without them.
• Feel for muscle – For a dog, run your hand along their spine and hips now and then, since muscle loss can matter more than weight⁶.

Even with good care, kidney disease keeps moving, and there usually comes a point where comfort gets harder to hold on to.

The research points to a few changes that tend to mean the disease is reaching its last stage, or that comfort is slipping.

• Not eating, even with help – A pet who has stopped eating despite medication and coaxing. In dogs, this went with the shortest time of all¹⁴.
• Losing weight and muscle quickly – Weight loss that’s speeding up, or muscle wasting away along the back and hips^5,​6.
• Vomiting most days – Nausea that medication no longer keeps under control.
• Staying dehydrated – Still dry, weak and tired even with extra fluids.
• Too weak for the basics – Struggling to reach the water bowl, the litter box or the door.
• Struggling with the daily care – Treatments that have become a daily battle for your pet¹⁷.
• A crisis – A sudden, severe flare-up, which becomes more likely in Stage 4⁴.

Cats in Stages 3 and 4 also scored lower on energy and emotional wellbeing than cats in the earlier stages¹¹, so a pet who seems flat or withdrawn may be telling you something too.

No single sign means it’s time, and tracking how your pet is doing over weeks tells you more than any one day. Our article on tracking your pet’s quality of life explains how. A free app like Hospet makes it easy to log vomiting, appetite and other changes and share them with your veterinarian; our short video “A free tool for tracking your pet’s quality of life” shows how it works. The section on when comfort isn’t enough anymore in our comfort care article looks at the bigger picture.

If you’re weighing what the daily care is asking of your pet, our veterinarians offer an in-home quality of life consultation. It’s a full, unrushed hour in your home, and you’ll leave with comfort care ideas, clear next steps and a report we can send to your regular veterinarian. When the signs start to add up, the decision ahead comes into view, and it brings questions of its own.

Every family’s situation is different, and our article on the euthanasia window walks through the factors that shape the timing for any pet. With kidney disease, a few deserve a closer look.

Kidney care can mean pills, fluids, special food and regular blood tests, sometimes for years. That care is part of your pet’s quality of life¹⁷, and it’s part of yours too. If the daily care is wearing you down, our article on anticipatory grief talks about the exhaustion so many caregivers feel, and why it’s nothing to feel guilty about.

Kidney disease can have ups and downs. After fluids, a change in medication or a stay in the hospital, a pet can perk up for a while, and a good day can make the decision feel wrong. In our webinar “When Is It Time? Understanding the Euthanasia Window”, we put it this way: “Yes, they’re having a good day today, but what did they have to go through last night to get to that good day? And when that starts to become a regular thing that owners are fighting with in their minds, that’s where a lot of owners decide to make the decision.” That’s why tracking good days and bad days over time matters: it shows you the trend, rather than just the day in front of you.

Not every turn comes slowly, though. In the last stage, sudden flare-ups become more likely⁴. A crisis can come on quickly, with a pet suddenly much sicker than the day before, and it can force a decision before a family feels ready. As we say in the same webinar, sometimes crises can come on unexpectedly, and we want to plan for that possibility. Our article on preparing for the emergency room can help you think through what you’d want if it happens at night or on a weekend.

Then there’s the cost. Ongoing kidney care costs money: blood tests, fluids, medications, special food and sometimes hospital stays. It’s okay for cost to shape the choices you make. As our article on the euthanasia window puts it, “Your pet cares about your love, not how much money you spend.” At the end of the day, you have to make the decisions that are best for your family, and cost being one of those factors says nothing about the bond between you and your pet or the love you share. Just because you could have done more doesn’t mean you didn’t do enough.

It can. Without euthanasia, the kidneys keep failing and waste keeps building up in the blood. The nausea, vomiting and loss of appetite that come with that buildup¹ usually get worse, and a pet who stops eating and drinking becomes more dehydrated and weaker. In Stage 4, the risk of a sudden crisis rises⁴. No study has measured how long this takes in pets or exactly what it feels like to them, so we can’t tell you what your pet’s path would look like, only that the signs described above tend to deepen rather than ease.

The veterinary end-of-life care guidelines ask veterinarians not to let a pet die naturally without considering euthanasia and making sure other measures to ease discomfort and distress are in place¹⁹. If you’re considering this path, please talk with your regular veterinarian about how to keep your pet comfortable, and what you’d do if they begin to suffer. Our article on letting a pet die naturally vs. hospice vs. euthanasia explains what each path involves.

Whichever way you lean, it can help to know what a planned goodbye would look like. If you’re considering a goodbye at home, What Happens During In-Home Euthanasia walks through the visit step by step, and our guide to preparing for an in-home euthanasia covers the practical side.

Kidney disease often gives families time: time to adjust, to try what helps, and to enjoy the good days. In the later stages, the focus shifts from slowing the disease to keeping your pet comfortable, and you’ll find yourself weighing what the care asks of your pet against what it gives them.

Lean on your regular veterinarian for the medical side, keep track of how your pet is doing over time, and please be gentle with yourself. Caring for a pet through a long illness is a lot of work, and however you decide, you’ll be deciding as someone who has looked after them every step of the way.

→ Keeping Your Pet Comfortable at Home
Practical comfort care for a sick or aging pet, from footing and bedding to eating, breathing and medications.

→ Tracking Your Pet’s Quality of Life: Why It Matters and How to Do It
Practical frameworks to objectively measure your pet’s comfort, happiness, and wellbeing over time.

→ The Euthanasia Window: Understanding When It’s Time
Why there’s no single “perfect moment,” and how to think about timing as a window rather than a moment.

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