Protein shakes are simple. Drop a couple scoops in. Pour water (or milk) up to the already-designated line, whirl it around; and you, sir, have a magical muscle-building elixir in the palm of your hands. 

Though sometimes it's not all that intuitive. You've got questions (like majority of men on the planet). Luckily, we've got answers. 

Here, Dawn Jackson Blatner, R.D.N., C.S.S.D., author of The Superfood Swapaddresses the most common protein shake queries so you can continue to make gains—without any negative side effects.

How many hours is a refrigerated protein shake good for?

"A refrigerated homemade shake can be kept safely for 72 hours," Blatner says. "However, because separation happens, you'll need to re-blend or shake before drinking.

So if you're only mixing powder and water or milk, you get the green light on prepping your shake the night before; it'll save you a few precious minutes when you're tearing through the house trying to find your gym membership card in the early morning.

But if you're blending in extra foods, think twice about leaving your smoothies and shakes overnight. "The quality, taste, and texture suffer—especially if fruits are added," Blatner says. It's still safe to drink, but why settle for a sub-par shake when you can blend up a fresh one?

How long can you keep a protein shake unrefrigerated? 

If you've been the ballsy type to blast through a workout, frantically shower, then suspiciously chug your shake as you scramble to work, wondering How long can milk stay good outside the fridge?, this answer's for you. "An unrefrigerated homemade shake can safely last 2 hours," Blatner says.

Our suggestion: Get a super-insulated travel mug proven to keep things cold for hours on end—any Yeti or Thermos will do—if you cut it close to the 2-hour mark. Alternatively, just ask if you can put your protein

Is it a terrible idea to mix protein powder with coffee? Does it mess with the integrity of the shake?

"Hot liquids can curdle and clump protein powder and, while this doesn't affect the protein quality, it’s just gross," Blatner says. "So if you want to add your protein powder to your coffee, mix it with some cold water first to dissolve it, then add the coffee," she suggests.

You can also mix it with iced coffee or opt for a coffee-flavored powder.

Can protein powder itself go bad?  

"Yes, a protein powder can go bad—most brands have recommended use-by dates and/or expiration dates," Blatner says.

So, uh, might want to check the ancient tubs you've been hoarding.

"It's best to store protein powder tightly closed in a cool, dry place," she adds. "Heat, moisture, and air can spoil protein powders and cause molding."