It is 11PM and a mother kitten just abandoned her baby newborn(?) kitten.*PLEASE HELP.)

It's 11PM and no stores are open to go get formula. This little kitten is practically dying and I don't know what to do. I want to help it so bad and it's so heart breaking. It looks to be maybe a month old. But it is the size of a week old kitten. If anyone at all could give me any advice at all to help me I would greatly appreciate it.

If the kitten is truly 4 weeks old, you don't have to panic.  Perhaps she has run out of milk for the kitten.  You can get kitten formula in the morning.  In the meantime, you can use half milk (or cream) and half water to get something into its belly if it is really hungry.  Are the eyes open?  They definitely should be. At this age, kittens will begin to eat on their own (kitten food softened a bit with warm water).  Keep it warm, against your skin is ideal or under a light bulb will do in a pinch 80-85 degrees (just make sure it isn't too hot, the kitten should feel warm).  You will probably have to stimulate it to pee and poo (wet a paper towel and gently touch it to the area and the kitten will go). The mother licks it to stimulate it and kittens also roll onto their backs sometimes if they need to go.  I am not an expert, but years of caring for abandoned kittens on a farm have taught me what to do in a pinch.  I'm sure some people will disagree with some of my advice, but just trying to help you out until the morning!  Good luck!!

She was very limp. Her eyes were open and she did not want anything food or water wise. She did potty on herself though. We put her outside and her mom did end up coming back for her. So I think she should be okay.