Inadequate hydration is a big problem in the summer months. The weather heats up, people sweat a lot and really just about everyone could stand to drink more.

And dehydration really can run the gamut. You might just need to drink an extra glass of water or two to make sure you’re feeling your best, but the situation can also be extreme and lead to life-threatening complications, like heatstroke. Research suggests that even mild dehydration — meaning you’ve lost 1% to 2% of your body’s water — can really hamper your daily functioning.

Unfortunately, knowing when you’re in the early stages of dehydration isn’t always easy because some of the more common signs aren’t ones people necessarily associate with how much water (or other fluids) they’re drinking.

So, as summer heats up, here are a few sneaky signs that you need to hydrate ASAP.

While this isn’t a guarantee ― bad breath doesn’t always mean dehydration ― it could be a sign, Melissa Leber, an emergency medicine physician at Mount Sinai Morningside in New York City, told HuffPost.

There is an underlying mechanism that links inadequate hydration and less-than-pleasant breath. When you’re dehydrated, you don’t produce as much saliva, which helps break down food and rinses it from your mouth.

“The reduced cleaning action of the saliva allows bacteria to grow, causing bad breath,” explains the University of Michigan Health System website. So if you notice your breath is a little stinky, it could be a red flag that you need to drink a glass or two of H2O.

Dry mouth can also be another potential sign of dehydration, though not always. (Other possible causes include certain medications or even nerve damage.) So if your mouth often feels sticky or parched, or you find that you constantly feel thirsty, it’s definitely worth checking in with your doctor.

Experts think one reason people get muscle cramps when they work out is dehydration and electrolyte depletion, which means your body doesn’t have enough key minerals like sodium and potassium. Those minerals help balance pH levels in your body and also control nervous system function.

But cramping from dehydration doesn’t just affect athletes. If you’re walking around on a hot day and start to feel muscle pain or tightness, it could be a sign you’re not drinking enough.

And the same is true if you start experiencing involuntary muscle spasms or painful charley horses. “We call it tetany,” explained Leber, who cautioned it’s definitely something to pay attention to.

Headaches are a really common sign of mild to moderate dehydration, and they can be either tolerable or intense.

Dehydration can also trigger migraine episodes, for reasons that aren’t fully understood. Researchers have noted that dehydration can actually temporarily shrink brain tissue, and that shrinkage may cause pain.

One way health professionals diagnose dehydration is by testing a patient’s urine to see if it’s too concentrated, Leber said. But it can also help to do an easy check at home.

“Simply look at the color of your urine,” the Mayo Clinic suggests. “If it’s pale yellow, you’re hydrated. If it’s a darker yellow, it’s time for a glass of water (or two).” In general, the more you drink, the clearer your pee should be.

But remember: Urine color can also change based on medications you might be on or particular foods you’re eating. So if you have any concerns, ask your doctor.

If you’re generally just feeling kind of crummy — think the aforementioned headaches along with feeling kind of dizzy, lightheaded or nauseated — your first instinct might be to assume you’ve caught a bug of some kind. But it could be hydration-related.

“Anything that’s flu-like could be dehydration,” Leber said, adding that people can also experience fever or chills, especially with more moderate or serious dehydration.

“You actually can feel pretty terrible,” she said.

Thirst and hunger cues both come, in part, from the hypothalamus, which is the region of your brain that controls these functions along with other things like body temperature. So if you find that you’re feeling hungry soon after eating, it’s worth considering whether the real culprit is thirst.

Also, keep in mind that some of the signs outlined in this list — as well as other signs of dehydration — cross over a fair amount with signs of hunger, so it’s understandable that people often get the two mixed up.

Staying hydrated is a really crucial part of maintaining energy throughout the day. Hydration helps your body deliver key nutrients to your cells, and keeps your organs doing what they really need to do. Not getting enough water to do these functions can make you feel like you’re dragging.

Plus, hydration can have a direct impact on sleep quality. “Hydration is important for most systems of the body, which is why dehydration can have diverse symptoms, including effects on sleep,” explains the Sleep Foundation.

The group cautions, however, against overdoing it. Excess hydration can cause people to wake up multiple times a night to pee, which can also lead to fatigue. Ultimately, the goal is balance.

There aren’t hard-and-fast rules about how much anyone should drink in a 24-hour period (and the six to eight glasses rule has been pooh-poohed by plenty of experts).

In general, people “should drink to thirst,” Leber recommended, meaning you should drink when you’re thirsty and stop when you’re not. Although Leber also noted thirst is not always a reliable indicator, particularly in older people who can have diminished sensitivity to thirst. And groups like the Mayo Clinic also warn that by the time you’re thirsty, you might already be mildly dehydrated.

In the end, it’s just important to make sure hydration is something you’re conscious of as you go throughout your days, and that you plan ahead. Keep a reusable water bottle with you, or even consider one with marked time goals. If you’re not a huge fan of plain ol’ H2O, consider herbal tea or water infused with fruit or herbs.

“You have to prepare more if you’re going to be out in the heat and sweating,” Leber said. “If you’re planning to spend any amount of time out in the sun, you need to prepare. Ideally, you would start preparing the day before by drinking some extra fluids.”