My darling Hedy is now 8 1/2 months old and weighs 6.8 pounds aka 3.1kg
Is that a healthy weight? Is she rather on the small side for her age?
Thanks in advance

Attached is a picture of Hedy while she was out from her spay.

Every kitty is different. Full grown female bengals weigh between 10 and 12 pounds, but there are many who exceed that weight. Your little Hedy is still growing and will continue to grow for another 15 months or so. A kitten requires much higher calorie intake due to their growing. You will see growth spurts with her. Your vet will keep tabs on her weight. But, it is truly unusual for a bengal to become overweight. They have way too much energy for that (although there was an overweight bengal on an episode of My Cat From Hell). From your photo, she looks fine to me, weight wise.

From the picture she looks fine.

Some things to watch for:
Underweight cats feel very boney, especially around the spine. A healthy kitten has lots of fat on the spine and it feels soft rather than boney.

Kittens for the first few months are around 1lb per month. After about 5 months it slows down for females. The weight sounds healthy generically.

Finally, underweight kittens can easily catch up with extra food. If you are concerned, offer her extra food. If she eats it, she'll use it to grow. As Sherry said, it's very rare for a Bengal to get overweight.

I think you should not base numbers to know if she's healthy or not. Look her physically, you can judge if she's healthy or not. If she eats and doing well then it's one factor that she's healthy.

Mine was just in for her spay at just shy of 6 months and she weighed in at 6lb 2oz. I feed her a small can a day and she gets all the dry she can eat for grazing. Mine has plenty of climbing items and a wheel to help her grow some muscles which seems to be working based on how hard it is to get her off my foot now.

How does your cat rate on this chart?

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The little monsters 3