TL;DR Don’t choose something with ultra-high amounts of sodium, carbohydrates, or sugar unless you need to based on your exercise levels or a sweat test.

Amy Brownstein, a registered dietitian nutritionist at MyNetDiary, says electrolytes are minerals that exist naturally in your body. These include magnesium, calcium, chloride, sodium, potassium, and phosphorous. The role of electrolytes is to help your body rehydrate or stay hydrated by helping your system actually absorb the water you drink.

Heather Gosnell, a pediatrician, sodium is the key ingredient for effective rehydration. She also says a little sugar and carbohydrates help your body absorb water but to avoid high-sugar drinks.

Electrolyte powders usually contain these, as well as the aforementioned minerals, all of which can help with absorption. But how can you know which powder is best for you?

Shelley Balls, RDN, says humans usually lose sodium when working out or spending time in hot temperatures and also that carbohydrates are important to help replenish and preserve muscle glycogen stores to prevent fatigue, especially if active for more than 30 minutes. Basically, if you’re working out a lot and not replenishing lost carbs, you’ll feel fatigued much faster. That’s especially true for intense workouts or long sporting events, in which case she recommends re-upping carbohydrates every 30 to 45 minutes. Sugars like glucose serve similar purposes, helping to replenish muscle glycogen as well.

If you’re just looking for supplements for day-to-day life or to soothe your hungover brain, you don’t need as high a concentration of sodium or carbohydrates in your electrolyte powder. Brownstein says to choose an option within the context of your daily habits and diet. Most people already consume the recommended 2,300 milligrams of sodium per day, she says, so if you’re not depleting sodium stores with intense exercise, you probably don’t need a powder with a high sodium content. The same is also true for sugar.

The best way to figure out exactly what you need is by undergoing a sweat test, which analyzes the contents of your sweat. But if that’s not a medical need, your best bet is to choose a powder that lives somewhere in the middle of ingredient concentration. That is, unless you’re sweating a ton, working out in high heat, or training in high altitudes, in which case, you should prioritize higher concentrations of sodium and sugar. Brownstein adds that if you notice white, chalky residue on your skin or clothes after working out, you might need to up your sodium intake.

When it comes to synthetic dyes, Balls says the right answer ultimately comes down to personal choice. Luckily, if you want to avoid these ingredients, many of our recommendations omit them.

To avoid stomach upset, Balls suggests looking for powders that are lower in magnesium (which can have a laxative effect in high amounts). She also says that because calcium and iron can interfere with the absorption of each another, it’s best to choose a powder that has balanced, lower amounts of the two supplements. Brownstein says that high sugar and sodium content can also upset some peoples’ stomachs, and that you should read the labels to help you avoid over-supplementing (or over-caffeinating). If something contains 100 percent of your daily recommended zinc content, for example, you want to make sure you’re not also taking a multivitamin with the same amount of zinc.

Balls says to look for a powder that includes the key electrolytes lost: sodium, potassium, magnesium, and calcium. She says, if possible, to avoid drinks with artificial sweeteners.

Hallie Zwibel, director of the Center for Sports Medicine at New York Institute of Technology, says “in addition to causing upset stomach and reduced fluid absorption, repeatedly consuming high-sugar foods and beverages can lead to diabetes, as well as potential weight gain.” He adds that “while electrolyte packets can help replenish essential minerals lost through sweat, they should not replace daily water intake.”