Isotonic, Hypotonic and Hypertonic Sports Drinks can be confusing, so we are here to help out.

As more people embrace fitness and nutritional supplements, the energy drink market has grown by leaps and bounds. Whether you’re pumping iron at the gym, running a marathon or simply looking for an energy boost at work, bright and shiny sports drinks are now easy to find at even the most basic grocery stores. In 2015, 199.7 million 192 oz. cases of sports beverages were sold in America. At first, these non-carbonated drinks were targeted toward athletes; now everyone from school kids to busy 9-to-5ers is gulping them down.

Most sports beverages out there have high carbohydrate content, designed to boost energy levels after a strenuous workout. When you lose electrolytes through sweating, it can cause muscle cramps and nausea. These drinks also typically come loaded with sodium, magnesium, potassium, calcium and other essential nutrients to get your electrolyte levels back on track.

But not all sports drinks are the same. Their carb content and other ingredients could differ, and it’s important to pick one that matches your exercise routine. Here’s a quick rundown of the differences between isotonic, hypotonic and hypertonic sports drinks.

Isotonic sports drinks

The salt and sugar concentrations in isotonic drinks are similar to the ratio you find in the human body—if the human body is healthy, that is. These drinks have a carb content that varies between 6% to 8%, including glucose. This allows for quicker absorption by a body that has been pushed to the limit by exercise. And the higher the carb content, the less need to urinate, which means isotonic drinks enhance your fluid retention.

One key study found that cyclists who were given an isotonic drink retained higher levels of electrolytes like calcium and magnesium, allowing them to make up for loss of these nutrients as they sweated it out. That’s one reason why isotonic drinks are the preferred choice for long- and middle-distance runners.

Hypotonic sports drinks

These drinks are meant for people who aren’t looking for a carb boost. The salt-sugar content of hypotonic drinks is lower than what you find in the human body. Jockeys and gymnasts prefer this drink because it optimizes fluid absorption, minus the carb increase. The ideal time for a hypotonic sports drink is after a strenuous workout. These drinks aim to keep dehydration, one of the main causes for sports-related fatigue, at bay.

For a sports drink to be properly absorbed by the gut, you need sodium. One study found that hypotonic drinks can have performance-enhancing capabilities if there’s sodium present in the mix. The same study found that the water from the hypotonic drink is absorbed quicker by the body, allowing for speedy rehydration.

Hypertonic sports drinks

If you’re looking to boost your body’s post-workout glycogen levels, a hypertonic drink will do the trick. These drinks contain higher concentrations of sugar, salt and carbs than the human body, making them an ideal choice for people engaging in ultra-strenuous physical activities.

Long-distance marathon runners, for instance, need higher carb replenishment. Hypertonic drinks contain >10% of this compound. Athletes usually consume hypertonic drinks after an exhaustive workout. If you’re consuming it during a workout, make sure you have an isotonic drink, as well.

What about good old H2O?

Water is the best rehydration option, but too much of it can cause an electrolyte imbalance in your body and impair nerve cell function. This rare, yet possible, condition is known as water intoxication. That’s where sports drinks are important. Because of their electrolyte and carb content, these drinks can give your body the ingredients it needs to replenish itself. A sports drink with the right mix of ingredients will also prevent over-hydration.

When you don’t need a sports drink

A sports drink isn’t needed if you’re indulging in less-strenuous workouts (<60 minutes). A University of California report found that people who take part in physical activity that lasts more than an hour are the one who will benefit most from a sports drink.

But the same report states that a large number of people who consume sports drinks don’t take part in any physical activity through the day. This just increases your calorie intake. Since sports drinks contain sugar, a less active person might be opening the door for weight gain by downing a bottle. These sports beverages also contain sodium; too much of this mineral and you’ll notice a spike in blood pressure. Like all supplements out there, even sports drinks need to be consumed in moderation—and along with exercise.

There’s no one-size-fits-all solution when it comes to post-workout rehydration. Your daily training duration, weather conditions, intensity level and overall weight are big factors in determining how much of a sports drink your body needs. A good way to stay on top of fluid loss is to take heed when your body is nearing fatigue levels. That way you’ll know exactly when to crack the seal of your favorite sports drink.