kitten wont keep food down

Hey there, I'm pretty new to this forum, actually I made this account for this reason.

My mom got me these two , now five week, old kittens. They are darling little Tabby/tortoiseshell crosses.

Ive had cats my whole life and never encountered this, My Boyfriend is a first time cat owner and loves them to piece. one of our girls will eat and then throw it back up a few hours later. They both have healthy appetites and both are eating the same food. Luna doesn't puke But Mars can't seem to keep it down. Every night now it seems she piles on my blankets.

It's not all the time it's kind of roulette at this point, the poor thing. She's so full of energy afterwards, wanting to play and cuddle so She's feeling alright I guess? I've tried changing her food to a different brand/flavor she seems to do okay with some and others get the same result.

What should I do?

Five weeks old ??? That's way too young to be away from their mother cat. They should still be being weaned by the mom cat.

Unfortunately that wasn't an option. What do I do? My next attempt was going to be grabbing kitten milk from the pet shop

Right ok it's not the normal cat milk from pet shops you need. It the kitten milk replacer you need like KMR or royal canin baby cat milk. It comes in a powder form and you make it up following the instructions. Put some in a dish and offer this to the kittens as well as cat food

You said she does okay with some foods and not others.  I would first just keep her on the ones she does well on.  Is she on wet food?  You could try mixing some of the KMR with the wet foods that she seems to be okay with.  That's how people often help a mom cat wean her kittens, though it isn't really necessary when the mom cat is doing a good job.  Have they been checked for parasites?  Kittens almost always have them.

Edit* Sorry I've been informed they are seven weeks.

They're on wet food right now , She's a very picky eater though as wel, like she won't eat if her food is cold kind of picky. I've kept her on the brand and flavor she likes But it seems like it's still happening (as I type this I've been up with my baby for three hours and it's seven in the morning ).

I'm a 24 year old student,so ita a bit hard for me to be home all the time, but when im not the boyfriend is and they seem to be doing the same. I'm not entirelllllyy sure what KMR is, though I'm a bit slow thanks to the time.

They've been checked and given their shots and all that. Apparently They're healthy as can be. That's why I'm stumped. I was thinking an allergy But I've tried the gluten and wheat free expensive stuff and it still has the same effect. Sometimes it will stay down and pretties it will be down for a few hours and right back up again.

Ah kitten milk replacer I got it. But as I've said there her sister is just fine, shell scarf down a whole can if I let her. They're on kitten wet food at the moment.

How many times a day are you feeding them ?? I would recommend ( because she keep throwing up ) feeding them little and often maybe 5-6 meals a day. It could be that she is just eating too much in one go.

t doesn't sound like she's over eating if it's taking several hours for her to throw up.  Usually if they overeat, they throw up almost immediately. 

You said you are feeding the same brand and flavor, pretty much.  What exactly are you feeding?  It could be it's too rich for a young kitten, or could be she has issues with one or some of the ingredients (likely). 

Another thing which I hate to think about is that she swallowed something she shouldn't have and now has a partial blockage.  That can result in vomiting hours after eating, although with that, I would think she would vomit after  EVERY meal, and thankfully that's not happening, right? 

she isnt throwing up after every meal, just after the 'dinner' one, ive changed her feeding schedule around and so far so good. they go at the food pretty hard, the both of them. ive been watching her lately and shes pooping regularly and eating/ behaving as she should. im a little lost, i wen and got her some KMR powder today it seems like she likes it so far, shes eaten it almost all day with no issues. im thinking maybe that food itself was too much for her, ive scaled it back a bit and offered her the replacement as an accompaniment and shes held her food all day but the last meal hasnt been delievered yet.

thank you everyone for you imput and helping with mars and her tummy aches. Shes reacted really well to the changed feeding schedule and the KMR powder, shes started keeping every meal down and even started playing longer. she sleeps through the night and im not waking up with her pukey noises anymore. im so relieved so thank you so much guys.