Senior Siamese cat crystal risk — diet advice

Urinary problems in cats deserve real attention — in male cats especially, blockages can become life-threatening within hours, but even in females, chronic crystal formation causes pain, bladder inflammation, and eventual kidney damage. Diet is one of the most powerful tools we have for prevention and management, and a vet check is essential if there's an active problem. To point you in the right direction: is your cat male or female, what symptoms are you noticing, has she seen a vet recently, and what are you currently feeding her?

That's actually a really common finding in older spayed females, and it's good your vet flagged it proactively rather than waiting for symptoms. The hormonal changes that accumulate over years after spaying can subtly shift urine pH and concentration in ways that favour crystal formation — particularly struvite and calcium oxalate, which frustratingly form at opposite ends of the pH spectrum. The fact that she's Siamese adds a layer too: the breed tends toward a more concentrated urine pattern. Can I ask — is she drinking reasonably well, and is the dry food she's on a standard adult kibble or something marketed as urinary support?

Right, so there are two things working against her at the moment: standard dry kibble has a low moisture content which concentrates urine and raises crystal risk significantly, and a supermarket adult formula won't be doing anything to manage urine pH or mineral balance. Given that your vet has already identified the risk and she's not in crisis, this is actually the ideal window to make a dietary change that could prevent a much more painful and expensive problem later. My clear recommendation here is Royal Canin Urinary S/O — specifically the wet food version as your primary feed, with the dry used as a smaller complement if you want to keep some kibble in the mix. S/O is formulated to create a urine environment that's genuinely hostile to both struvite and oxalate crystals simultaneously, which is exactly what you need when the vet hasn't confirmed which type she's prone to. It also has controlled mineral levels and is designed to encourage drinking through palatability. For a 9-year-old Siamese with a proactive vet flag, this is the most defensible choice on the market. The pouches are widely available on Amazon UK — the 85g adult urinary S/O pouches are cost-effective in bulk packs.

Transition gradually — over 7 to 10 days is ideal. Start with about 25% new food mixed into the current food, then move to 50/50 around day four, then 75% new by day seven, and fully switched by day ten. Cats are notoriously sensitive to food changes, and Siamese in particular can dig their heels in if the swap feels abrupt. One practical tip: serve the new food slightly warmed the first few times — it increases the aroma and most cats find it more appealing than straight from the fridge. Once she's fully on S/O, you should aim for wet food making up the majority of her diet. If you do keep some dry S/O in rotation, make sure fresh water is always available in multiple spots — some cats drink better from a wide shallow bowl or a running fountain.

Don't leave it to hope — book a follow-up urinalysis in about three months. A urine dipstick and sediment check will tell you whether her pH has moved into a safer range and whether crystal load has reduced. It's a straightforward test, not expensive, and it gives you real data rather than guesswork. Your vet already knows the baseline from this visit, so a three-month recheck gives you a meaningful comparison. If crystals have reduced or resolved, you'll know the diet is doing its job. If not, the vet may want to consider a prescription version or look more closely at whether there's an underlying metabolic component. The diet change is the right first move — verification is what makes it properly managed rather than just hopeful.