The first time I teetered on the verge of dehydration was on a mid-July day in South Carolina on vacation.

I was rollerblading (yes, rollerblading, don’t judge) around the neighbourhood I was visiting—just cruising around, nothing crazy, so I didn’t bring any water with me.

About an hour in, I suddenly felt dizzy. I sat down under a tree in the shade for 15 minutes to get my bearings, then rolled home to enjoy a long stretch of A/C and sweet tea.

I’ve since had some scary episodes during long bike rides, but the fact is you don’t have to be pushing hard or going long to succumb to dehydration.

“It’s normal to experience mild dehydration during exercise,” says Rob Pickels, physiology director at CU Sports Medicine and Performance Center in Boulder, Colorado—especially if you’re in the heat and sweating.

“However, prolonged moderate dehydration or severe dehydration can be detrimental to your health; especially your kidney function,” he says.

You already know you need water when you feel thirsty, but there are less obvious signs that you’re on your way to serious dehydration. Here’s what Pickels warns to watch for.

A faster heart rate can be a sign of dehydration

Heart rate goes up with intensity, and it will tend to drift with long exercise. However, if you’re seeing heart rates that are 15 to 20 beats higher than you’d expect, it could be your heart is compensating for reduced blood volume (aka dehydration) by beating faster.

Dizziness can be a sign of dehydration

You know how your head swims a bit when you suddenly stand from a sitting position? It’s called postural hypotension, and it’s the result of blood not reaching your head quickly enough as you change positions, thanks to low blood volume.

If you start feeling that at the gym when switching from seated to standing workouts, it could be a sign of dehydration.

Saggy skin can be a sign of dehydration

Technically called “decreased skin turgor,” when the skin on the back of your hand doesn’t snap back from being pinched, it’s a sign you need more fluids, stat.

“With normal hydration, the pinched skin should return back to normal essentially immediately,” says Pickels.

With moderate to severe dehydration, it will be slow to return.

“Try it now (I know you are) by pinching your skin for 2 to 3 seconds and then letting go. That’s your baseline,” he says.

Smelly urine can be a sign of dehydration

If nature calls and it smells like you’ve wandered into a bus station bathroom, that’s another good sign to drink more.

“A strong urine smell can be a sign of dehydration,” says Pickels.

Of course, it’s still good that you have to pee at this point, since once you hit severe dehydration, urine production decreases dramatically. Avoid slipping into that next stage by boosting your fluid intake as soon as possible.

The article How To Know if You’re Dangerously Dehydrated  originally ran on