When you’re looking for a store-bought meal shake, first determine what need you’re filling. Are you simply trying to increase your protein intake? Is your goal to lose or gain weight? Or maybe you’re just looking for a balanced meal replacement.

If you answered “yes” to the first question, you’ll want to look for a low carb, high protein shake option. This means looking for a shake with between 20 and 40 grams of protein, but fewer than 10 grams of carbs and typically less than 5-10 grams of fat. A shake like this should typically be around 200 calories or less. Think of shakes like this the same way you would a chicken breast. Because they’re low in fat, carbs, and overall calories, they won’t likely keep you full for very long on their own, but they can be a great way to add protein to a meal or snack that already contains carbs and fat but lacks enough protein. The protein shakes our dietitians often recommend for this purpose are brands like Premier Protein or Fairlife Nutrition Plan. Pro tip: Throw in a serving of peanut butter and a banana alongside one of these shakes to add a healthy source of fat and carbs. This combo will come out to around 35 grams of protein, 35 grams of carbs, 15 grams of fat, and works as an excellent pre-workout snack. Other shake examples like this include Core Power shakes, Orgain protein shakes, or Protality protein shakes.

If you’re trying to lose weight, many of the shakes above are a great choice, but for more nuanced reasons. For example, people using GLP-1 medications or who have undergone bariatric surgery may experience early fullness and be unable to completely finish meals. As a result, it’s crucial that these patients prioritize getting enough protein first to prevent muscle wasting while they pursue their medically supervised weight loss. A shake that is high in protein while simultaneously being low in carbs and fat provides a protein-dense supplement that can be consumed quickly before fullness sets in.

While all the shakes listed above are excellent sources of protein, they often lack sufficient amounts of other macronutrients. If you’re looking for a meal replacement shake, you’ll want to find a higher calorie shake with a balanced ratio of carbohydrates, fat, protein, and fiber. Everyone’s nutrition needs are different, but a good meal replacement shake should be between 300 to 600 calories with 15 to 30 grams of protein, 30 to 50 grams of carbs, 15 to 30 grams of fat, and around 5 grams of fiber. Keep in mind that not everyone will feel full after drinking their calories, so feel free to beef up your meal replacement shake with a piece of fruit, veggies and dip, or some cheese and crackers. Some examples of shakes intended for meal replacement are Soylent Shakes and Kate Farms Nutrition Plan. Be aware that many shakes marketed as “meal replacement” are far too low in calories to qualify as a meal. If using a shake with less than 300 calories, we recommend using it as a “snack” only or adding multiple other components to the meal to make up for the missing calorie needs.

Or, you may be looking at shakes for a very different reason from the ones listed above — as a supplement to gain weight. Some shakes are intended for individuals who struggle to maintain weight due to a chronic condition or who have illnesses that impair their absorption of food, reduce their appetite, or lessen their stomach capacity. In cases like these, calorie density is key. Here, the name of the game is to find out a shake’s calorie-to-ounce ratio. A good shake for weight gain should have 300 or more calories for every 12 ounces of liquid. Shakes like these will often have a higher fat content because fat is more calorie dense than carbs or protein. If you’re trying to put on weight, these shakes can be used as a meal replacement for low appetite days or as a daily supplement on top of your regular meals. Great examples of shakes that fit this role include Boost Plus, Boost Very High Calorie, or Ensure Plus.

No matter what kind of shake you’re looking for, remember that while shakes are great tools to add convenience to your life, it is important to use them as part of a healthy diet and not to replace full, balanced meals.