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Cat kidney guide

Kidney Disease / Appetite & Hydration Changes in Cats

What to notice, what to track, and what to ask your vet if your senior cat is eating less, drinking more, losing weight, vomiting, hiding, or just seeming “off.”

Your job is not to diagnose kidney disease at home. It is to notice what is changing, know which signs should not wait, document the patterns, and bring that information to your veterinarian.

Start with urgent signsWhat to track
Start here
1

Notice the pattern

Appetite, thirst, weight, litter box, and behavior changes can be subtle in cats.

2

Know what cannot wait

Not eating, repeated vomiting, toxin exposure, or straining with little/no urine should prompt a call.

3

Bring clearer notes

Tracking helps your vet understand what changed before the appointment.

It often starts small.Your cat leaves food in the bowl. She drinks from the faucet more than she used to. The litter clumps look bigger. She spends more time tucked away somewhere quiet. Nothing dramatic, just a sense that something is different.

That quiet, hard-to-pin-down feeling is worth trusting. Cats are very good at hiding illness, and in a senior cat, subtle changes in appetite, thirst, weight, litter box habits, or behavior can be the first sign that something needs attention.

One possible cause is chronic kidney disease, which is common in older cats. But these same signs can also come from hyperthyroidism, diabetes, dental pain, nausea, urinary disease, or another condition. They do not tell you the cause on their own.

This guide can help you

✓Recognize appetite, thirst, weight, litter box, and behavior changes.
✓Know which signs should prompt same-day or emergency care.
✓Document what you are seeing before a vet visit.
✓Prepare better questions for your veterinarian.

This guide cannot

!Diagnose kidney disease or tell you how severe the problem is.
!Replace bloodwork, urinalysis, blood pressure checks, or veterinary care.
!Provide a treatment plan or determine the cause at home.
One urgent exception to flag right away: if your cat is straining to urinate, making repeated trips to the litter box, crying in the box, or producing little or no urine, do not assume that is kidney disease. That pattern can be a urinary emergency, especially in male cats, and should be seen right away.
If this is happening now

Some changes can wait for a call. Others should not wait.

When you are unsure, call. Describing what you are seeing is often enough for a veterinary team to tell you whether to come in now or monitor closely.

Call your veterinarian today

!Has eaten nothing for about a day.
!Has been eating very little for more than a day.
!Is eating less and also vomiting, hiding, weak, or known to have kidney disease.
!Is drinking much more than usual, has larger urine clumps, is losing weight, or seems nauseous, withdrawn, or “off.”

Call an emergency clinic now

!Repeated vomiting, cannot keep water down, collapse, severe weakness, or sudden worsening.
!Hiding and unwilling to come out, especially with other signs.
!Straining to urinate, crying in the litter box, or repeated trips with little or no urine.
!Possible lily exposure, antifreeze, human medication, another toxin, seizures, sudden disorientation, or sudden blindness.
The litter box distinction matters.
Larger urine clumps or more urine overall can happen with kidney disease, diabetes, hyperthyroidism, and other chronic conditions. Repeated litter box trips with little or no urine, straining, crying, or obvious pain are different and may be a urinary emergency, especially in male cats.
Signs caregivers may notice

Kidney-related changes in cats often show up as small pattern changes.

You know your cat’s normal better than anyone. A cluster of these changes is worth paying attention to.

Eating and nausea

✓Eating less, finishing meals slowly, sniffing food and walking away, or becoming suddenly “picky.”
✓Lip licking, drooling, swallowing repeatedly, or vomiting.

Water and litter box

✓Drinking more or choosing faucets, cups, tubs, or unusual places.
✓Larger urine clumps, more frequent urination, accidents, constipation, or straining.

Weight and body

✓Weight loss or muscle loss over the spine, hips, or back legs.
✓A duller coat, grooming less, lower energy, or weakness.

Behavior changes

✓Hiding more, irritability, or seeming “off.”
✓Subtle changes that are easy to dismiss as “just old age.”

Mouth signs

✓Bad breath, drooling, dropping food, or discomfort around eating.
✓Mouth pain can overlap with appetite changes.

Other possible causes

!Hyperthyroidism, diabetes, dental pain, pancreatitis, constipation, urinary disease, stress, or other illness can look similar.
Do not dismiss new changes as aging.
Aging may make some problems more common, but new changes in appetite, thirst, weight, grooming, litter box habits, or behavior deserve a real look.
Appetite and hydration

A cat who is not eating is not necessarily “just picky.”

Nausea and dehydration can be quiet in cats, and both can affect appetite, energy, and litter box patterns.

Nausea can be subtle

A nauseated cat may sniff food and walk away, hover near the bowl, lick their lips, drool, swallow repeatedly, or eat only a few bites before stopping.

Pressure can backfire

Repeatedly pushing a nauseated cat toward food, or trying to force food without veterinary guidance, can create food aversion.

Drinking more is not proof

A cat drinking more is not automatically well-hydrated. Increased thirst can mean the body is trying to compensate for water loss through urine.

Notice both sides

Watch water intake and urine output together: bowl emptying faster, larger clumps, more box visits, or accidents.

Access matters

Arthritis, weakness, nausea, bowl placement, or litter box access can affect how much a senior cat drinks or uses the box.

Call rather than struggle alone

If your cat is eating nothing for about a day, eating very little for more than a day, vomiting, hiding, weak, or medically fragile, call your veterinarian.

Why appetite loss is different in cats
You do not need to panic over one missed meal, but a cat eating nothing for about a day, or very little for more than a day, deserves a call. Cats can develop a serious liver problem called hepatic lipidosis, or fatty liver, when they stop eating, especially if illness, nausea, or rapid weight loss is involved. Appetite loss often needs medical help. It is not a character flaw in your cat, and it is not a failure in you.
Before calling or visiting the vet

What to document before calling or going in

Your notes can genuinely help your veterinarian. Many of these changes happen at home over days or weeks.

Appetite and food response

✓When appetite changed, what your cat is eating and refusing, and whether she sniffs food and walks away.

Water and litter box

✓Water intake changes, clump size and frequency, accidents, or constipation.
!Any repeated trips, straining, crying, or little/no urine.

Vomiting and stool

✓Vomiting frequency and what it looks like, constipation, or stool changes.

Weight and behavior

✓Weight changes, muscle loss, hiding, energy, grooming, and behavior changes.

Meds and exposure

✓Medications, supplements, recent diet changes, and possible toxin or lily exposure.

Safe visuals

✓Photos or videos can help, but do not delay urgent care to collect them.
Daily tracking

What to track day to day

Daily tracking helps you and your veterinarian see patterns over time. With chronic illness, the trend across days or weeks is often more useful than one isolated day.

The tracker does not diagnose, score, monitor, or interpret medical data. Exams and your veterinarian’s guidance still guide medical decisions.

Use it to log:

Appetite
Water intake
Vomiting / nausea
Stool / constipation
Litter box changes
Weight
Medications
Energy
Hiding / behavior

Use Notes for details like “refused wet food but ate treats,” “larger urine clumps today,” “vomited after breakfast,” “lip licking at the bowl,” “hid under the bed,” or “straining in the litter box.”

Tracking should never delay urgent or emergency care. Call first and log later.

Request beta access
Vet conversation

Questions to ask your vet

You do not need everything in one visit. Choose the questions that fit the moment and keep the rest for follow-up.

If you are overwhelmed, start with these three:

1

How urgent is this based on what I am seeing?

2

What should I watch for over the next day or two?

3

What signs mean I should call back or go to emergency care?

Do you recommend bloodwork and a urinalysis?
Should we check urine concentration and blood pressure?
What do BUN, creatinine, SDMA, phosphorus, potassium, and urine protein mean in general terms?
Could hyperthyroidism, diabetes, dental disease, pancreatitis, constipation, urinary disease, or another condition be contributing?
Could nausea, stomach upset, mouth pain, or constipation be affecting appetite?
What are the safest ways to support appetite and hydration?
Would a kidney diet be appropriate, and how can we avoid food aversion if diet changes are needed?
If fluids are appropriate, what would that involve?
What is realistic for our family in terms of cost, time, stress, transportation, and what can be managed at home?
After veterinary guidance

Daily care considerations after veterinary guidance

These are not steps to start on your own. Diet, medication, fluids, and supplements should be guided by your veterinary team.

Diet changes

Your vet may discuss a therapeutic kidney diet and gradual transitions to reduce food refusal.

Moisture support

Wet food, water placement, and moisture support may be part of the plan after veterinary guidance.

Appetite and nausea

Appetite or nausea support may be prescribed if your cat is not eating well.

Monitoring

Blood pressure, phosphorus, potassium, urine, bloodwork, and weight may need follow-up.

Fluids

Subcutaneous fluids may be discussed if appropriate, but should be prescribed and taught by your veterinary team.

Home access

Water station placement, easier litter box access, comfortable resting areas, and stress reduction can matter.

A meaningful amount of time is possible for some cats.
The outlook depends on stage, other health conditions, appetite, hydration, and the individual cat. Your veterinarian can give you the clearest sense of what is realistic.
Common worries

Common worries you may be carrying

“Is this just old age?”

No one can tell that from home. Appetite, thirst, weight, litter box, grooming, and hiding changes deserve veterinary attention rather than being filed under “she’s just getting old.”

“Is my cat picky or nauseous?”

It can be hard to tell. Sniffing food and walking away, lip licking, drooling, hovering near the bowl, or seeming interested but not eating can be nausea signs.

“She’s drinking a lot, so is she hydrated?”

Not necessarily. More drinking can be a sign of the problem, not proof that hydration is okay.

“Am I failing if I can’t get my cat to eat?”

No. Appetite loss often needs medical help. You are not failing because you cannot solve nausea or illness by willpower.

“What if I can’t afford everything?”

It is okay to ask your veterinarian what is most urgent, what can be staged, and what options exist.

“What if they have good days and bad days?”

That can happen with chronic illness. Tracking patterns over time helps your veterinarian understand the overall direction.

Trusted resources

Trusted resources for deeper reading

These resources are for deeper reading. They do not replace veterinary care.

Vet school overview

Cornell Feline Health Center — Chronic Kidney Disease

A clear vet-school overview of feline chronic kidney disease for caregivers.

Visit Cornell
Cat-specific guidance

International Cat Care — CKD in Cats

Cat-specific caregiver guidance from a feline-focused organization.

Visit iCatCare
Veterinary staging

International Renal Interest Society

The staging framework many veterinarians use for kidney disease.

Visit IRIS
Owner overview

VCA Animal Hospitals — Chronic Kidney Disease in Cats

An accessible overview of signs, diagnosis, and care considerations.

Visit VCA
Reference manual

Merck — Noninfectious Diseases of the Urinary System

A reliable cat-owner reference that includes chronic kidney disease and urinary conditions.

Visit Merck
Senior cat care

FelineVMA / AAFP — Senior Care Guidelines

Guidance on caring for aging cats and recognizing health changes.

Visit FelineVMA
Toxin emergency

FDA — Lovely Lilies and Curious Cats

Explains why lily exposure is a true emergency for cats.

Visit FDA
Poison help
Pet Poison Helpline: 1-855-764-7661. ASPCA Animal Poison Control: 1-888-426-4435. Both are available 24/7; a consultation fee may apply.
If your cat's situation looks a little different, these guides may fit better:
Straining to Pee / Urinary Blockage in CatsHyperthyroidism in Senior CatsDiabetes in CatsBrowse the full Resource Library

A final note

This guide is a starting point for caregivers, not a diagnosis or treatment plan. Appetite, thirst, weight, litter box, and behavior changes in a senior cat can have several causes. The only way to know what you are dealing with, and what might help, is to have your cat evaluated.

Notice the patterns. Watch for urgent signs. Bring what you are seeing to your veterinarian. And be gentle with yourself along the way. Noticing that something is “off” is part of caring well.

Last reviewed: June 2026