Potassium supplements: who actually needs them

Does my cat with kidney disease need potassium?

Maybe, and it's genuinely worth checking, because low potassium is common in kidney cats and it's one of the few problems in this disease where the fix produces a visible change in a matter of days.

But this is also the drug on the whole list I'm most careful with, because potassium can go wrong in both directions, and the direction flips as the disease advances. So the short answer is: it depends on her blood level, and it needs rechecking.

Why kidney cats run low

Potassium is what muscle uses to work properly. It's tightly regulated in a healthy cat, and the kidneys do most of the regulating.

Damaged kidneys leak it. She's producing more urine than she should, and potassium goes out with it. She's also often eating less than she used to, so less is coming in. The two together are why low potassium, called hypokalemia, shows up so regularly in the earlier and middle stages.

What low potassium looks like at home

This is worth knowing by sight, because it's one of the few kidney problems with a genuinely distinctive sign.

She holds her head and neck oddly low. Chin dropped toward her chest, neck bent downward, as though her head has become too heavy. That's called ventroflexion, and in a cat it points hard at low potassium. It looks strange enough that most owners mention it unprompted.

Alongside that: weakness and wobbliness, often described as walking as though the floor is uneven. Reluctance to jump onto things she's always jumped onto. A general flatness. Poor appetite, which loops back and makes it worse.

The part that's usually explained badly

Read this bit twice, because it's the reason I won't let potassium be a home decision.

Low potassium is the common problem in the earlier and middle stages. Kidneys leak it, she goes low, a supplement fixes it.

High potassium happens in late-stage disease, and it's dangerous. When the kidneys are failing badly enough that she's producing very little urine, potassium stops leaving and builds up instead. High potassium, hyperkalemia, affects the heart's rhythm. That's not a comfort issue, that's an emergency.

So the same cat, over the course of her illness, can need potassium and then need it stopped. A dose that was exactly right in stage 2 can be actively harmful in late stage 4.

Which gives one hard rule: potassium is decided on a rechecked blood value. Never on symptoms, never on last year's prescription, and never adjusted at home. If she's on it and she's advancing, her level needs checking at every recheck, and the dose may need to come down or come off.

Two things also raise potassium alongside late-stage disease, worth knowing because they can arrive together: an ACE inhibitor like benazepril, and dehydration. If she's on a protein-loss drug and her potassium is drifting up, that combination is why your vet is watching it.

What she'll be prescribed

Potassium gluconate is the standard, in a form made for cats: a gel you can put on a paw or mix into food, a powder that mixes into wet food, or a tablet. The gel and powder are usually easier, and mixing into food avoids the whole argument.

Notes that matter:

• Give it with food. Better tolerated and less likely to upset her stomach.
• Don't use a human potassium product. They're dosed for a person, and some formulations irritate a cat's stomach or worse. This isn't an area to improvise.
• Split the daily dose if your vet suggests it. Twice daily is gentler than one large dose.
• A kidney diet may be enough on its own. Therapeutic renal diets have extra potassium added for exactly this reason, and plenty of cats hold a normal level on the diet alone. The supplement is for cats who are still low despite it.

When to recheck

One to two weeks after starting, to confirm the dose is right. Then at every routine recheck, because the target moves as she does.

That's not a clinic padding the bill. Potassium is a dose-found drug, and the first dose is a reasonable estimate from her weight and her level, not a known quantity. The recheck is what turns the estimate into a dose.

Where this sits

Potassium is one line on her panel, and the panel makes more sense read as a whole. That's her bloodwork, translated, where potassium sits alongside phosphorus, creatinine and the rest.

If she's weak and flat and her potassium is normal, the usual suspects are dehydration, anemia in the later stages, or simply not eating enough, which is nearly always nausea rather than fussiness.