CKD Stage 1 in Cats: Early Signs, Diagnosis & What to Do Next

If you're reading this, your vet has probably just told you your cat has “Stage 1 kidney disease” — and you're confused, because your cat seems perfectly fine. That confusion is completely normal. Stage 1 chronic kidney disease (CKD) is almost always discovered by accident, during routine bloodwork for something else entirely — a dental cleaning, a senior wellness exam, or an unrelated illness.

The good news: Stage 1 is the earliest possible point of intervention. Cats diagnosed this early can often remain stable for years with nothing more than careful monitoring and small lifestyle adjustments. This article explains exactly what Stage 1 means, how it's diagnosed, and what you should — and shouldn't — do next.

What Does Stage 1 CKD Actually Mean?

The International Renal Interest Society (IRIS) stages CKD based on bloodwork and other evidence of kidney damage. Stage 1 is defined as having some identifiable sign of kidney disease while blood creatinine and SDMA levels remain within their normal ranges. In practical terms, this usually means one of the following was found:

• SDMA slightly elevated (18–25 μg/dL) while creatinine is still normal
• Protein in the urine (a high UPC ratio) without other explanation
• Abnormal kidney imaging — irregular shape, small size, or poor cortico-medullary definition on ultrasound
• High blood pressure with no other cause

The critical thing to understand: at Stage 1, the kidneys are already damaged, but they're still compensating. Cats have enormous kidney reserve — they can lose roughly two-thirds of their kidney function before creatinine starts to climb. That's why the earliest stages are invisible on basic lab work.

Why Stage 1 Is So Easy to Miss

Your cat will almost certainly show no symptoms at Stage 1. No increased drinking, no weight loss, no change in appetite. The kidneys are still filtering well enough that waste products haven't built up to noticeable levels. This is why CKD in cats is so often diagnosed late — by the time symptoms appear, the disease has usually progressed to Stage 2 or 3.

This also means that if your cat was caught at Stage 1, you're genuinely ahead of the curve. The window for early intervention — the period where you can make the biggest difference with the least effort — is exactly where you are now.

How Stage 1 Is Diagnosed

Your vet will typically run a combination of tests to confirm and characterize the disease:

• Full blood panel including creatinine, BUN, and SDMA — SDMA detects kidney decline earlier than creatinine alone
• Urinalysis — urine specific gravity (concentration) and protein levels (UPC ratio)
• Blood pressure measurement — high blood pressure is both a cause and a consequence of kidney damage
• Abdominal ultrasound — to look at kidney size, shape, and structure

If your cat is newly diagnosed and you want to understand the numbers on the bloodwork, our guide to creatinine, SDMA, and IRIS staging walks through each value in plain English. You can also plug your cat's numbers into our free IRIS staging calculator.

Do I Need to Switch to a Renal Diet at Stage 1?

This is the most common question we hear — and the answer is usually “not yet, but start planning.” IRIS guidelines for Stage 1 typically focus on monitoring and early supportive care rather than an immediate prescription diet. Many vets recommend waiting until Stage 2 before switching to a renal food, because early diet change can be hard on appetite and the benefit at Stage 1 is less established.

That said, there's no harm in starting to move toward a lower-phosphorus, higher-moisture diet now — especially wet food, which supports hydration. Ask your vet whether a gradual transition makes sense for your cat. When the time comes, our comparison of Hill's k/d vs Royal Canin Renal will help you choose.

What You Should Do Now

Stage 1 management is about slowing progression and catching changes early. Here's the practical checklist:

• Recheck bloodwork in 3–6 months — your vet will tell you the right interval; the goal is to establish a trend, not a single snapshot
• Maximize hydration — wet food, a water fountain, multiple bowls. Hydration is the cheapest medicine in CKD care
• Weigh your cat monthly — an accurate home scale; weight loss is the single most reliable early warning sign
• Monitor blood pressure and urine protein — these are the two “silent” accelerants of CKD progression
• Keep a symptom log — drinking, urination, appetite, activity. Changes are easier to catch when you have a baseline

What Happens Next?

Cats can remain at Stage 1 for a long time — months to years. The rate of progression varies enormously between individuals, and it depends heavily on the underlying cause and how well secondary factors (blood pressure, proteinuria) are controlled. Your job now is simple: stay consistent with monitoring, keep your cat hydrated, and build a relationship with your vet around this disease specifically, because you'll be managing it together for a long time.

If your cat has already moved past Stage 1, our guide to CKD Stage 2: life expectancy, diet, and daily care covers the next phase in detail.