How do you know you’re in love, really? That depends on who you ask. Anecdotal signs you’re in love abound, but thanks to modern science there are surefire ways to spot signs you’re in love and possibly on the road to marriage. First-of-their-kind brain imaging studies done in 2012 revealed that love might be more of a habit-forming reaction to the euphoria-inducing chemicals your brain releases when you’re with a person you’re attracted to. So, one of the first signs you’re in love is you might find yourself constantly craving quality time with your girlfriend or boyfriend (and those feel-good chemicals).

Here are 6 additional signs you’re really, really in love, according to science.

When being with them makes you feel like you just simultaneously ate a chocolate bar and finished a marathon.

According to a 2010 study about signs you’re in love, the exact chemical cocktail released into your brain when you’re in love includes adrenaline (that heart-pumping chemical you feel when you’re nervous), dopamine (one of the chemicals that helps us understand rewards and pleasure) and oxytocin (the sweet hormone released when we get hugs).

When you suddenly can’t finish a sentence.

Dry mouth, tongue-tied and flustered around a certain someone? Those are actually signs you’re in love, thanks to your body’s natural regulation of norepinephrine, a chemical which causes your blood pressure to go up and your words to get all jumbled when you get googly-eyed.

When you really, really like the way they smell.

Scent has long been one of the ways scientists and lay people determine signs you’re in love. Whether it’s scented hormones called pheromones signaling our readiness for love or wearing your love’s unwashed T-shirt, smell can be a powerful indicator of your attachment.

When your tolerance for physical pain increases.

Another benefit of oxytocin, one of the natural chemicals released when you’re in love? A higher tolerance for pain. It’s the same chemical that helps parents exhibit super-human strength to rescue their kids, and can also go into overdrive when you’re in love, resulting in less physical pain. So, that no-pain dream-like state some feel when they’re in love can actually be very real.

When you think you have the flu around them.

Sweaty palms, nausea, sleeplessness? Some of the most unpleasant aspects of bugs and viruses actually mirror signs you’re in love. Multiple studies have found that people start to feel sick when they are first in love, thanks in part to the blood-pressure-raising chemical your body starts to pump out.

When you constantly feel like you’re a few glasses in.

Think back to the last time you had a few drinks. You were probably much more relaxed, talkative and willing to get up on stage for karaoke than normal. If you start to feel this way when you’re around your girlfriend or boyfriend, or when you think about them, it probably isn’t the wine, but rather yet another side effect of oxytocin. The same chemical that your body releases when you’re snuggling with your puppy starts to majorly up production when you’re in love and can make you feel less reserved and more extroverted.

The good news is these physical symptoms of being in love are temporary. If you don’t fancy a lifetime of tongue-tied, sweaty headiness, just wait until you’re more comfortable with your love and you, your heart rate and your brain chemicals will go back to normal.