Need to gain weight

Need to gain weight  

Originally Answered: Need to gain weight

Hello as a new member I I am looking for help with my 16-year-old tabby, Sampson.
His weight dropped from 14 pounds to 9 pounds he’s been tested for hyperthyroid ok but pancreas and kidneys are poor .. his B12 and vitamin D are very low...our vet has him on a supplement regimen and he seems hungry a lot (at night) but picks and wastes the food (Purina complete dry Friskies pate and slices wet). She gave me Mirtazapine which makes him weird but he gained weight .45lb which he lost when off.
Thank you for your time

Dr. Joanna Woodnutt, MRCVS
Originally Answered: Need to gain weight

Hi @Lynnmkelly,

Senior cats can be tricky, and it sounds like yours has got plenty going on! it's hard to give any specific recommendations because there's so much happening for him, and without a hands-on exam and his blood results I can't be sure what's happening. Weight loss is for one of two reasons - not enough calories going in, or too many calories being expended. Diseases like hyperthyroidism and diabetes aside, the first is the most common in senior cats, especially those with a problem that causes inappetence or nausea. (There's also muscle wastage, which can be seen with a variety of diseases and is common in senior cats, but since it can be hard for people to tell the two apart I usually lump this in together with the weight loss category).

It sounds like your vet has done some exams but what's not clear is whether they've ruled out all of the causes of calorie need increase or not, and whether they've looked at muscle wastage vs weight loss, so I'm afraid I can't give you any advice on that. From what you've said though, it does sound like he's not getting enough calories in (he's hungry and he's messing with his food rather than eating it, as well as the mirtazapine helped him some).

Here are some thoughts to take to your vet and discuss.

1) Dental disease and oral pain - worth looking at, as messing with the food is a symptom. Did your vets mention anything about his teeth? Sometimes with senior cats with concurrent illness it can be difficult to treat dental disease but it may be necessary if this is the cause of his weight loss. A pain relief trial may also help with deciding on this.

2) Kidney problems are common in old cats, and whilst they can't be cured they can often be managed on a prescription renal diet. Did your vet discuss putting him on a renal diet? It might be worth considering, as this has balanced protein and phosphorus to protect his kidneys and prevent weight loss. It may also reduce nausea, which can cause him to play with his food rather than eat it.

3) An energy-dense senior diet like the 'senior consult' range from Royal Canin might be appropriate so he doesn't need to eat much to get his calories. However, this needs to be considered by your vet as it's a balance between the best diet for his kidneys and the best diet for his weight loss. Your vet can consult with any of the prescription pet food companies to get their opinion on balancing these concerns for him.


I hope some of those thoughts help. With his problems, I wouldn't advise making any changes to his diet until you've discussed it with your vet. Even adding in calorie-dense treats could be risky as it might upset his renal disease further.

I hope that helps,

Dr Joanna Woodnutt MRCVS

Veterinary Surgeon



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