A cat that starts crying in the small hours, in a house where nothing has changed, is usually doing it for a medical reason. In an older cat this is one of the most useful signs you will ever notice, and one of the most ignored.
The senior care guidelines name the problem in one line: owners and vets may blame it on the cat just being old. They go on to say that changes appear gradually and can look like a cat simply adapting, which is exactly why nobody books an appointment for it.
The hyperthyroidism guidelines list increased vocalization directly among the clinical signs, alongside weight loss, a big appetite, drinking more, restlessness and a coat that stops looking cared for. The classic patient is over eight years old, and the disease is diagnosed in somewhere between 1.5 and 11.4 percent of older cats worldwide. It is the most common hormonal disease of middle-aged and older cats, and it is treatable.
Cornell links the two plainly, saying night-time vocalizing is relatively common in cats with an overactive thyroid or with high blood pressure. The reason to take that seriously is what else high blood pressure does: the feline hypertension guidelines report that many cats with severe damage to the eye arrive already blind, from retinas that have detached or bled, and that those changes are often permanent. They recommend blood pressure is checked at least yearly from age seven, and every six to twelve months from age eleven. It is a painless check and most owners have never been offered it.
The acute pain guidelines list growling, groaning, howling and hissing among pain behaviors, and note that failing to recognize pain is the main reason cats go untreated for it. Joint disease is extremely common in older cats and frequently undiagnosed.
This is the one people jump to, and it belongs last rather than first. A 2022 survey run through Colorado State's veterinary teaching hospital collected 615 completed owner questionnaires and classified 80 cats as showing cognitive dysfunction. The most common sign in that group was inappropriate vocalization, reported in 40 percent of them.
But the diagnosis is made by elimination, not by recognising it. The senior care guidelines say cognitive dysfunction is ultimately a diagnosis of exclusion of medical and environmental causes. A 2010 review says the same: when the behavior is identified, the diagnosis can only be made by ruling out all potential medical causes. Cornell adds that the signs usually become noticeable from about ten years old, and lists among them altered sleeping and waking cycles, staring at walls, and unprompted loud vocalizing.
Nearly every page on this subject says that deaf cats yowl because they cannot hear themselves. We went looking for a professional source for it and did not find one. It may well be true, and it is repeated everywhere, but we are not going to print it as a fact with nothing behind it. If your cat has lost its hearing, mention it to the vet as part of the picture, rather than as the explanation.
If everything comes back clear, then it is worth looking at the night itself: a cat left alone for the first time in years, a change in feeding time, a light or a noise. But that comes after the blood test, not instead of it.