Rechecks: what your vet tests, and why

How often does a cat with kidney disease need blood tests?

There's a number floating around the internet, usually every six months, and it's wrong for about half of cats. This is one of the questions where your cat's specifics genuinely matter, so the most useful thing I can do is show you what sets the interval and let you ask for hers by name.

The reason for that last row: those drugs are dose-found, not dose-known. Your vet makes a sound first estimate from her weight and her numbers, and the recheck is what turns the estimate into a dose. Skipping it isn't saving a visit. It's leaving her on a guess.

What a complete recheck looks like

Blood alone is not a recheck. Here's the full list, and it's worth having on your phone.

Her weight. The honest scoreboard, and it costs nothing. A cat who has lost a quarter of a pound since last time is telling you something no blood value says as plainly.

A blood panel, including creatinine and SDMA (waste products, and what her stage is based on), phosphorus (the value that most changes how she feels), potassium (which can go wrong in both directions), and a red cell count or hematocrit, because anemia creeps in later on.

A urine sample. Specific gravity, to see whether she can still concentrate, and a UPC, urine protein to creatinine ratio, to see whether her filters are leaking. Protein loss makes the disease move faster and it has a specific treatment your vet won't prescribe without the number.

A blood pressure reading, if your vet has the equipment. Between one in five and one in three kidney cats is hypertensive, and it usually causes no symptom at all until it causes a permanent one, most often sudden blindness. It's worth having where it can be had. It also needs a machine that a lot of practices don't own, mine included, and the reading is genuinely hard to get right in a cat, which is covered on the blood pressure page.

A physical exam, including her mouth. A painful tooth or an ulcer explains a lot of "she's just not eating much", and it gets missed when the appointment quietly becomes a blood draw.

The one that gets skipped

Urine. Consistently, everywhere, and not out of laziness: it takes longer, it costs more, and on a busy day blood alone feels like enough.

It's also the test most likely to change what happens next, and unlike blood pressure it needs no special equipment at all. So if the plan is a blood draw and a goodbye, that's a fair moment to ask: what about her urine.

Blood pressure belongs in the same conversation, with the caveat that it depends on what's in the building. If your vet has a machine, ask. If not, ask what they'd rather you watched for.

When a number gets worse

Before you accept a jump as the disease progressing, know how many things push these numbers up temporarily.

Dehydration is the big one, and it can move a cat a whole stage on paper. A silent kidney infection. Constipation. A recent meal, for BUN. A new medication, including any anti-inflammatory meant for a person. And simply the car and the exam room, which lift blood pressure and glucose in a stressed cat.

So a single bad sheet is a reason to look, not a verdict. Two sensible responses: repeat the test once she's settled and properly hydrated, and hunt for the treatable thing sitting on top. That's covered on the crisis page, including the urine culture worth asking for by name.

The trend is the thing. One value is a snapshot taken in an unrepresentative moment. Four values across a year is a story, and the story is what your vet is treating.

Make the visit worth more than it costs

Small things that buy a much better recheck for no extra money.

Bring your notebook. Weights with dates, what her appetite has done, any vomiting, what the box has looked like. Four weeks of that beats anything you'll remember on the spot, and it changes decisions. What's worth recording is on the monitoring page.

Bring the actual bottles, not a list from memory. Doses, strengths, and how long she's genuinely been on each.

Ask about collecting urine at home, using the non-absorbent litter most clinics will give you. It saves a needle and some stress, though a culture still needs collecting at the clinic to be reliable.

Say your budget out loud. If money is tight, ask which parts matter most this time. There's nearly always a sensible reduced version, and a vet who knows the constraint can build one. A vet who doesn't will build the full thing, and you'll find out at the desk.

What you're watching over time

Four things, in rough order of importance:

• Weight, holding or falling
• Phosphorus, against her stage target rather than the lab's range
• Creatinine and SDMA, direction of travel across several visits
• Red cells, drifting down in the later stages

A cat whose weight is steady and whose phosphorus is controlled is being managed well, almost regardless of what her creatinine reads. That combination is the goal, and confirming it is what a recheck is for.

For what each individual value means, see her bloodwork, translated. For what the overall picture means about time, life expectancy is as honest as I can make it.