Most fitness-loving people know how important it is to stay hydrated in the summer. In fact, many of us carry around giant water bottles to try to increase our water intake! What you might not know is that even being mildly dehydrated can muddle your thinking and affect your mood enough to throw off your game—and sabotage your workout. Here are 5 signs that you might be dehydrated.

1. Headaches

Our bodies are made up of mostly water, so when we don’t give our bodies the water they need, they have trouble functioning the right way. A dehydration headache is a surefire sign that you need to drink up. Depending on the person, this headache could be as mild as a dull ache, or as intense as a full migraine.

2. Sugar cravings

This is an unexpected one, we know! Your liver needs water to turn carbs into glycogen, which helps your body create energy – so a lack of fluids can make your body call out for sugar!

3. Racing heart

When you’re dehydrated, your heart has to work harder to pump blood around your body, which causes your heart rate to increase. If you feel your heart beating unusually fast when you aren’t working out, it may be a sign you need to rest and rehydrate.

4. Light-headedness

Dehydration can cause a drop in blood pressure, which can make you feel light-headed. Feeling dizzy during a workout can be dangerous, so if you start feeling dizzy or light-headed, take a break and drink some water.

5. The tried-and-true sign

If you’re urinating less often (the average person takes 4-10 trips to the restroom in a 24-hour period), or it’s a darker color than usual—this is a good sign that you’re dehydrated.