Cats are the ultimate poker players; they’ve evolved to hide pain and illness so well that by the time you notice something is wrong, they’re often quite sick. Whether you're wrangling a chaotic kitten or keeping a watchful eye on a dignified senior, you need to know the red flags. From "just a cold" to "my kidneys are failing," here is the data you actually need to keep your cat thriving.
Upper Respiratory Infections (URI)
Think of these as the feline version of a nasty cold or flu. They spread like wildfire in multi-cat households or shelters. Staying on top of common cat health problems is your first line of defense.
What's causing it?
Most URI cases in cats are driven by Feline Herpesvirus (FHV-1) — up to 80% of exposed cats develop a lifelong infection, according to the Cornell Feline Health Center — with Feline Calicivirus (FCV) picking up most of the rest. Sometimes bacteria like Bordetella or Chlamydia join the party too. Cats catch these just like we do: sneezing on each other, sharing water bowls, or even just touching a surface an infected cat rubbed against.
Symptoms to watch for
The Basics:
- Constant sneezing and clear runny noses.
- Squinty, watery eyes (conjunctivitis).
- Looking a bit "blah" and skipping a meal or two.
The Red Flags:
- Thick yellow or green snot.
- A fever over 103°F.
- Total refusal to eat.
- Mouth-breathing or struggling for air—this is an emergency.
How to help them feel better
Home Comforts:
- Fire up a humidifier to help them breathe.
- Warm up some smelly wet food; if they can't smell it, they won't eat it.
- Use a warm, damp cloth to keep their face clean of crusty discharge.
The Vet's Toolkit:
- Antibiotics: For when bacteria move in.
- Antivirals: Like Famciclovir for heavy hitters like Herpes.
- Eye Meds: Necessary if they develop painful corneal ulcers.
Staying ahead of it
Keep those FVRCP shots up to date. If one cat starts sneezing, move them to a "recovery room" away from the others immediately.
From the clinic
A 4-month-old shelter kitten came in for a week of sneezing, thick green eye discharge, and refusing to eat. On exam his temperature was 104°F, both nostrils were crusted shut with mucopurulent discharge, and fluorescein staining confirmed a superficial corneal ulcer in one eye. An FHV-1 PCR came back positive. We started oral Famciclovir, an ophthalmic antiviral, and syringe-fed a recovery diet until his appetite returned on day three. The ulcer healed in ten days and he went to his foster home a week later, eating on his own and breathing cleanly through his nose.
Chronic Kidney Disease (CKD)
Cat kidneys are notoriously fragile. According to the Cornell Feline Health Center, chronic kidney disease affects up to 40% of cats over age 10 and as many as 80% of cats over age 15 — making it one of the most common diagnoses in senior feline medicine. For a deeper dive on diagnosis and treatment, see our full guide to Feline Chronic Kidney Disease.
Why does it happen?
Usually, it's just wear and tear from age. Sometimes it's genetics (looking at you, Persians and Siamese), or a tragic encounter with a lily or antifreeze.
The Warning Signs
Early on, you might just notice your cat is visiting the water bowl more often and peeing giant clumps in the litter box. They might lose a little weight or look a bit "scruffy."
As it gets worse, you'll see muscle loss, frequent vomiting, and a distinct, ammonia-like "uremic breath."
Diagnosis and Management
Vets use blood work to check BUN, Creatinine, and SDMA — the early warning system. Creatinine doesn't rise until roughly 75% of kidney function is lost, while SDMA elevations can be detected after only about 40% of function is gone, catching CKD months or years earlier.
Once kidney disease is confirmed, vets stage it using the IRIS staging system (International Renal Interest Society):
- Stage 1: No azotemia yet, but early signs of kidney damage — poor urine concentration, abnormal renal imaging, or persistent proteinuria.
- Stage 2: Mild azotemia. Cats often still look and act normal; this is the sweet spot for catching CKD early with SDMA. Mean survival is typically 2–3 years with management.
- Stage 3: Moderate azotemia. Clinical signs (weight loss, vomiting, poor appetite) are usually obvious.
- Stage 4: Severe azotemia. Uremic crisis risk is high; mean survival is under six months.
While you can't "cure" CKD, you can manage it for years with:
- Renal Diets: Low-phosphorus, moderate-protein prescription foods are non-negotiable — Cornell notes that cats on prescription kidney diets can live 2–3 times longer than those on regular food.
- Hydration: Subcutaneous fluids are a game-changer for keeping them feeling good.
- Meds: Phosphate binders, appetite stimulants, or blood-pressure drugs (telmisartan is FDA-approved for hypertension in cats).
From the clinic
A 14-year-old domestic shorthair was brought in because his owner noticed he'd been losing weight for two months and was draining his water bowl every night. Blood work showed a creatinine of 2.4 mg/dL and an SDMA of 22 — IRIS Stage 2. We started a renal diet, taught the owner to give subcutaneous fluids every other day, and a year later the cat was still chasing his wand toy and stable on the same protocol. The takeaway: CKD caught early is a very different disease from CKD caught late.
Feline Diabetes Mellitus
Diabetes is one of the most common endocrine diseases in cats, with an estimated 1 in 100 to 1 in 500 cats diagnosed during their lifetime, according to Cornell. The biggest modifiable risk factor? Being overweight — obese cats are up to four times more likely to develop diabetes than ideal-weight cats.
The Signs
Look for the "Classic Triad":
- Excessive drinking and peeing.
- Ravenous hunger.
- Weight loss despite the fact they're eating everything in sight.
Life with a Diabetic Cat
It sounds scary, but it's manageable. Most cats need insulin injections — Cornell lists Glargine (long-acting) and ProZinc as two of the most commonly used insulins in cats — along with a strict high-protein, low-carb diet. The insulin type, starting dose, and schedule must be chosen by your veterinarian for your individual cat. Never adjust insulin without veterinary guidance — an overdose can cause life-threatening hypoglycemia (weakness, seizures, coma). Many Type II diabetic cats can even go into remission if you catch it early, get their weight under control, and start insulin therapy promptly.
From the clinic
A 12-year-old, 7-kg neutered male came in for a 1.5-kg weight loss over two months despite a ravenous appetite, plus flooding the litter box and a sudden switch to drinking from the bathtub. Blood glucose was 420 mg/dL and fructosamine was elevated, confirming persistent hyperglycemia. He went home on 1 unit of glargine every 12 hours alongside a strict low-carb canned diet, with home glucose curves at 2 and 6 weeks. By week 8, fructosamine had normalized and his insulin dose was being tapered; he achieved diabetic remission four months after diagnosis and has stayed off insulin for over a year on diet alone.
Hyperthyroidism
Common in older cats, hyperthyroidism is caused by an overproduction of thyroid hormones (T3 and T4), most often from a benign adenoma on one or both thyroid glands, according to the Cornell Feline Health Center.
What it looks like
If your 14-year-old cat is suddenly acting like a kitten, screaming for food at 3 AM, and losing weight despite eating like a horse, get their thyroid checked. They might also have a racing heart, vomiting or diarrhea, and a greasy, unkempt coat.
Treatment
- Radioactive Iodine (I-131): The "one-and-done" cure. Cornell reports it cures hyperthyroidism in roughly 95% of cases within three months and is the gold standard when available.
- Daily Meds: Methimazole pills or transdermal gel — lifelong, usually twice-daily dosing, with periodic blood tests to monitor thyroid and kidney function.
- Diet: Prescription iodine-restricted food (somewhat controversial — discuss with your vet).
- Surgery: Thyroidectomy is effective but rarely chosen because medication and I-131 work just as well with less risk.
From the clinic
A 15-year-old spayed female was brought in for nighttime yowling, an 800-g weight loss despite eating well, and intermittent vomiting. Total T4 came back at 11.2 µg/dL (reference range 0.8–4.0), with no significant renal or cardiac disease on screening bloodwork. After discussing radioactive iodine, medication, and diet, the owner chose transdermal methimazole applied to the inner ear twice daily, with rechecks at 2 and 6 weeks. T4 normalized by week 6, vomiting resolved, and she had regained 400 g by month three — a small but meaningful gain in a senior cat.
Feline Lower Urinary Tract Disease (FLUTD)
This is an umbrella term for bladder and urethra issues, including Cat UTIs. The Cornell Feline Health Center describes FLUTD as the #1 reason cats visit veterinary practices, with causes ranging from stress-related idiopathic cystitis to urinary stones to urethral plugs.
The major danger: If a male cat can't pee, it's a life-threatening blockage. According to the Cornell Feline Health Center, complete urethral obstruction can kill a cat in as little as 24–48 hours if not relieved. If your cat is straining, crying in the litter box, or producing nothing, go to the ER right now.
From the clinic
A 6-year-old neutered male came in for straining in the litter box with no urine produced for 12 hours. He was hiding under the bed, panting, and crying when his belly was touched. Blood work showed dangerously high potassium and a crashing heart rate. We passed a urinary catheter under sedation, flushed his bladder, and kept him hospitalized for three days on IV fluids. He's now on a moisture-rich diet and a stress-reduction plan, and has stayed unobstructed for over two years.
Dental Disease
By three years of age, most cats have some level of periodontal disease — often invisible to owners until it smells like a trash can or your cat starts dropping food while eating. The 2019 AAHA Dental Care Guidelines stress that untreated periodontal disease causes chronic pain, infection, and inflammation that can damage the heart, liver, and kidneys over time. A professional cleaning under anesthesia (not "anesthesia-free dentistry") is the standard of care — and far cheaper than treating what an infected mouth eventually damages downstream.
When to stop reading and call the vet
Emergency: Go Now
- Gasping for air or blue-tinted gums.
- Straining with no urine output (especially male cats).
- Seizures.
- They ate a leaf from a lily bouquet.
- Sudden collapse or unresponsiveness.
- Suspected ingestion of antifreeze, ibuprofen, acetaminophen, or any rodenticide.
Proactive Care
For healthy adults, one checkup a year is fine. For the seniors (7+), go twice a year. Cats are stoic — yearly blood work (BUN, creatinine, SDMA, T4, glucose) often catches what they're trying to hide.
A note on the AI assistant
The chat assistant available on this site is a general-purpose tool for cat-care questions. It does not provide veterinary diagnoses, prescribe medications, or replace an in-person exam. If your cat is showing any of the emergency signs above, skip the chat and head straight to your nearest emergency clinic.