There comes a time in all new parents’ lives when you’re so tired that you’re operating on automatic. You feed your newborn a bottle and they fall asleep in their bedside bassinet mid-meal. You groggily put the bottle down and fall asleep yourself — for what feels like 5 minutes.

Now baby’s woken up hungry again and you’re wondering if you can just pick up where you left off. But you look at the clock — and instead of 5 minutes, it’s been 65. Is that half-eaten bottle of formula a foot away still good?

This is just one scenario where a formula question might come to mind, but there are lots of others — so if formula rules have you scratching your head, you’re not alone. Let’s get you some answers, STAT.

Check the package instructions

We’ll give you some general guidelines, but always check your specific formula’s packaging for mixing, storing, and use instructions. There can be slight variations among brands — and even within brands!

Once you mix water and formula powder to create that magical elixir that nourishes your sweet babe, the countdown clock starts ticking. As a general rule, the bottle will last for 2 hours at room temperature, untouched and unheated.

But check the label instructions — for some brands, manufacturer instructions say a bottle is only considered safe for 1 hour at room temperature once mixed. It may depend on whether the brand is following American Academy of Pediatrics or Centers for Disease Control and Prevention guidelines.

Related: 13 of the best baby formulas

Yes, as long as your baby doesn’t drink from the bottle.

An unused bottle of formula mixed from powder can last up to 24 hours in the fridge. That’s why many parents opt to make a larger batch of formula in the morning and portion out into bottles — or pour into bottles as needed — for use throughout the day.

These parents know that a crying baby is often a hungry-right-now baby who doesn’t want to wait for you to mix a bottle.

Your fridge temp should be 40°F (4.4°C) or lower.

As an aside, it’s not recommended that you freeze formula. It can change the texture and doesn’t extend the period of time during which the formula is still good. If you’re new to formula after breastfeeding, it’s important to know the guidelines are different in this and other regards.

Related: How long can breast milk sit out?

No. In fact, if your little one has had some of a bottle but doesn’t want the rest, you should dump it within an hour. Don’t put it in the fridge for later use.

Milk-based products are notorious for growing bacteria. Once your baby has drunk from a bottle, bacteria is introduced and the formula shouldn’t be saved. (Incidentally, this is also why you shouldn’t drink directly from the milk carton, even if it’s just a swig after that chocolate chip cookie.)

Nope. Again, bacteria is the issue here — and bacteria thrive even more once given a nice warm environment to grow in.

Something else to know: If you’ve warmed up a bottle, our previous 2-hour guideline for untouched formula doesn’t apply. A heated bottle should be used within 1 hour, and any remaining should be poured down the sink after that time. This applies to formulas prepared from powder as well as concentrates and ready-to-drink options.

Generally, you should use up powdered formula within a month of opening the container. We found this to be the guideline on labels for popular brands like Similac and Enfamil as well as organic alternatives from Happy Baby Organics and Earth’s Best. This shouldn’t be a problem, given your little one’s voracious appetite!

Related: 10 organic formula options worth trying (and where to buy them)

Fortunately, you don’t have to guess at this one or remember the day you bought the formula. A sealed container of formula, whether powder, concentrate, or ready-to-drink, will always have an expiration date on it. In most cases, you’ll find this printed on the bottom.

The powdered formulas we looked at in our local store had dates more than a year away. So if you find yourself with unopened containers after your baby transitions off formula, at least you’ll be prepared for any upcoming zombie apocalypse.

Store sealed containers in a cool, dry place and avoid exposure to extreme temperatures.

All the rules surrounding formula can seem a little nitpicky, but remember it’s your baby’s delicate tummy you’re dealing with and the guidelines suddenly become incredibly doable. And you’ll get the hang of how much your baby eats pretty quickly, decreasing or even eliminating the amount of formula that ends up down the drain.

“When it doubt, dump it out” is a good rule of thumb here. But like all things baby, you’ve got this and will soon be running on automatic — though we can’t promise you’ll never doze off after preparing a bottle!