Whether you want to bulk up, slim down, or make it through your 3:00 p.m. meeting without your stomach growling, protein shakes can help you achieve your fitness and nutrition goals. But with so many variables—type of protein, brand, liquid, mix-ins—protein shakes can go wrong really fast. Strengthen your shake with these expert-approved guidelines.

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Time It Right
Protein shakes are great alongside or in place of the occasional meal (don't have time to cook?), but they are meant for after hard workouts, says Jim White, R.D., spokesperson for the Academy of Nutrition … Dietetics. That's when your muscles need their blend of carbohydrates and protein for recovery. If you want to pack in some protein before your workout, make sure you finish it off at least an hour before you enter the gym, he says.

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Drink Whey for Workout Recovery
When it comes to building calorie-torching muscle, whey protein is king, White says. It's the fastest-absorbing protein powder, and it packs the highest levels of leucine, an amino acid that's vital to muscle growth.

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Before Bed, Sip Casein
Casein takes its time leaving your stomach and making its way to your muscles, so it can be a good option when you want a meal replacement that will keep you full for hours or a bedtime beverage that will keep your muscles fed all night long, White says.

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Just Add Water
To keep your shake's calorie count low—after all, most of your calories should come from whole, chewable foods—the only liquid you need in your shake is water, says Jillian Spector, a certified nutrition and wellness consultant. Or, if you like things slushy, ice. White even recommends drinking a straight powder-and-water blend with every meal to up your plate's protein content.

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Mix in Your Meal
Speaking of food, fruits, flaxseed, nut butters, greens, Greek yogurt, oats, and avocado all make for vitamin- and mineral-packed mix-ins for a thicker, heartier shake, Spector says. You can even add coffee grounds for an extra jolt before your workout, White says.

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Know Your Ratios
For workout performance and recovery, your exact blend of carbohydrates and protein matters. A 4:1 ratio of carbs to protein is optimum after your workout to spur muscle and energy recovery, White says. A good guideline is 25 grams of protein and 100 grams of carbs. If you are fueling up for your workout, opt for a 1:1 ratio. It'll be easier on your GI tract during exercise, he says.

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