I like to think of myself as a calm, level-headed individual, but take away my food for more than a few hours and it’s going to get ugly.

At least twice a year, my brother threatens to get a me a T-shirt or coffee mug with sayings like, “Hangry: A state of anger caused by lack of food creating irrational and erratic emotion” or “I’m sorry for what I said when I was hangry.”

As much as I hate to admit it, my older sibling has seen his fair share of my hunger management issues in his time. I like to think of myself as a calm, level-headed individual, but take away my food for more than a few hours and it’s going to get ugly. It’s to the point where my friends and family will secretly bring extra snacks if they think we won’t be eating for a while.

I’m not alone. Hanger — the linguistic mashup of hunger and anger — isn’t just a handy excuse for being snippy. It’s a real phenomenon (and not just because it has its own hashtag). When you get hungry your blood sugar dips. The amount of glucose, your brain’s main fuel source, is diminished. Your brain is completely dependent on glucose to function. When it’s not getting enough glucose, your brain can struggle with energy-intensive tasks like behaving appropriately or remembering that you actually love the friend who just told you the restaurant has an hour-long wait.

Shaking, weakness, and feeling fatigued are all signs your blood sugar has dropped, according to Leah Groppo, a clinical dietitian at Stanford Health Care. If your stomach is rumbling and you’re starting to get irritable, you’re probably not getting enough glucose to your brain, she notes.

Those aren’t the only signs you’re hangry. The following are likely to happen if you don’t get a granola bar in your system ASAP.

You really aren’t yourself when you’re hungry. More accurately, you really aren’t your well-controlled self when you’re hungry. Between snapping at everyone in sight and gorging on all the donuts in the breakroom, hanger can make you lose all self-control.

If you ever find yourself angry at the entire world — especially the people in your direct vicinity — you might just be hungry.

It’s hard to rationalize when you’re hungry, but it turns out your hormones are upping the ante. When your blood sugar drops far enough, your brain sends signals to your body to start releasing more glucose into the bloodstream. One of the ways your body does this is by secreting adrenaline, the fight-or-flight hormone, and cortisol, the hormone we most commonly associate with stress. This means you may feel stressed or anxious, even if there’s nothing happening outside of your body to warrant it.

Don’t you dare tell me we’re out of coconut milk! How are we ever going to survive?

Much like watching the Food Network while running at the gym, hanger has a tendency to make you obsess about food until you finally sit down to eat.

I’m not typically a jealous person. But I can barely contain myself when I see someone eating steaming french fries or a flakey pastry when I’m hangry. Daydreams of running off with a slice of a stranger’s pizza are not unheard of!

It’s not surprising that when your brain isn’t getting enough fuel, you have trouble maintaining normal cognitive function. A small study found that acute low blood sugar can interrupt brain function and make cognitive tasks more difficult.

Don’t beat yourself up over the stale crackers or the lint-covered protein bar that’s been in your bag for a year. We’ve all been there.

If you notice the people around you are slowly backing up, there’s a chance your hanger is showing. Not only are you frightening your co-workers, but you may also be prone to making mistakes you wouldn’t otherwise. In other words, hanger probably isn’t going to earn you any raves on your performance review.

Research has shown that you’re more likely to get into an argument with your sweetheart when you’re hungry. Since we’re more likely to act out or be aggressive towards the people we’re closest to, it’s not uncommon that your significant other takes the brunt of your hanger. One small study found that people who were hungry were more likely to stick pins into a voodoo doll that represented their spouse. Yikes! Nothing good can come from this.

While your brain relies on glucose, every cell in your body needs it to function properly. When your blood sugar drops, your cells are starved for energy. Hunger often comes with a side of fatigue.

It turns out the damage from shopping while hungry isn’t just limited to the grocery store. According to one study, you’re more likely to buy more items from any store and spend more money when you’re hungry. Even your wallet feels your hunger pains.

Eat something. And maybe apologize.

For best results, eat a well-balanced meal or snack that includes protein, carbohydrates, and fat. This will help balance out your blood sugar and turn you back into your regular, friendly self. The box of donuts or bag of chips may make you feel better in the short term, but they’ll also rapidly send you right back into the throes of hanger.

Mandy Ferreira is a writer and editor in the San Francisco Bay Area. She’s passionate about health, fitness, and sustainable living. She’s currently obsessed with running, Olympic lifting, and yoga, but she also swims, cycles, and does just about everything else she can. You can keep up with her on her blog (treading-lightly.com) and on Twitter (@mandyfer1).