She gave birth yesterday around noon the kittwns were eating just fine. This morning I got up to check on them & the runt was sleeping away from mom Where the kitten was snuggled up against her. The kitten was cold & feels limp & weak. I tried to get her to nurse but she just keeps on sleeping. Should I be worried? Should I run out & get her formula? Please help

The first thing to consider here is warmth, if the kitten has not had the benefit of moms' body heat and has become hypothermic, she needs to be warmed back up.
You can throw a towel in the microwave (not for too long, it will burn) depending on the wattage of your oven I would start at 30 seconds and test it, wrap the kitten in it.
Get that going and get back to me I'll be waiting for your response.

Perhaps I was mistaken in thinking you were still on line. I was trying to get that info to you ASAP, I hope that you saw it and acted quickly, now for the rest of the answer.

If you have a rectal thermometer take the kittens temp, normal is about 101. I know it is a tiny place you have to invade, you will need to use lubrication, liquid anti-bacterial soap will suffice.
Continue trying to warm him up, he could also be hypoglycemic (low blood sugar) if he has not nursed during the night. To help correct this if you have Karo syrup, or even pancake syrup you can place some on your finger and rub it on his gums and tongue.
This info is meant to hopefully stabilize him until you can get him to the vet, because, of course, there could be other things going on.
I would definitely get some kitten replacement milk to have on hand and make sure mom and kittens are in a warm, draft free area.
I know this will not be what you want to hear, but one thing to consider here is a failure to thrive or simply Mom knowing something that you can't possibly be aware of.
Sometimes mother nature seems cruel, but often times canine and feline moms will push a babe aside for some reason unknown to us.

Thank you so much! As aoon as I put her in the warm towel she started to meow. I'm still concerned that she's not eating enough. The 1st kitten is latching on every chance he gets. Do I run out & buy #2 a bottle & formula? Or am I just over reacting?

Good job, we must have been typing at the same time.
Yes, go get replacement milk and a nurser, try to encourage her to nurse from mom as much as possible.
Even if you don't have to use it, it will be better to have it there.

Just a reminder, most nursers do not have the hole already in the nipple you will have to poke the hole in it yourself, make sure you check the directions.
Good luck I'm glad she is doing a little better

Thank you so much! I will keep you posted

Just wanted to update that little Meeyuki didn't make it :( Thank you for your help

I'm so sorry to hear that.
Kittens are so tiny and have little reserve.
Thank you for trying and doing what you could for her.