Quick answer

Whenever it helps you reach your daily total. In a meta-analysis, protein taken within an hour of a workout added no significant strength or size once total protein was counted. Studies of muscle building used 20 to 40 g servings spread every 3 to 4 hours, and a slow protein before bed.^1,2,3

Key facts

20 g of whey taken just before or just after lifting raised muscle protein building by a similar amount.³
Across 65 trials, protein added lean mass whatever time of day it was taken.⁴
Bedtime studies used 27.5 to 40 g of casein, a slowly digested milk protein.²
The ISSN calls the best time largely a matter of what you tolerate, since benefits came from protein taken before or after a workout.³

Before or after a workout?

A meta-analysis of randomized trials found that protein taken within an hour before or after exercise did not significantly add strength or muscle size; total daily protein was the strongest predictor of muscle gain.^1,2

Sports nutrition groups advise about 0.3 g of high-quality protein per kg of body weight (about 20 g for a 150 lb person) within 2 hours after exercise, then every 3 to 5 hours.²

Both fit the evidence. If a shake right after training is convenient, it matches the guidance; if not, a meal with protein in the next few hours does the same job, because muscle stays responsive for about a day.^2,3

Spread across the day

The ISSN suggests spreading protein across the day in servings every 3 to 4 hours.³

Muscle stays more responsive to protein for about 24 hours after resistance exercise, and NIH notes that muscle protein building rises for up to a day or two.^2,3

For a 70 kg adult, 0.25 g per kg is about 18 g per serving. Four meals or shakes of 20 to 30 g each, spaced through the day, add up to 80 to 120 g, inside the range advised for people who train.³

Before bed

In studies of people who lift weights, a bedtime drink of 27.5 to 40 g of casein, a slowly digested milk protein, raised muscle protein building overnight.^2,3

Those studies used casein, which digests slowly; it kept amino acids raised in the blood through the night. Bedtime studies of pea or other plant proteins were not found for this page, so whether they act the same way is not known.²

Rest days and days without a workout

Your daily target does not change on rest days. The ISSN's general advice is at least 20 to 25 g of protein, about 0.25 g per kg, with each main meal, and no more than 3 to 4 hours between meals.³

Fast and slow proteins

After 20 g of protein on an empty stomach, essential amino acids in the blood peaked about 30 to 50 minutes later in a study of 15 active men.⁵

Whey, egg white and soy are digested quickly; casein and fattier cuts of meat more slowly. Speed matters for a single serving, but over a full day of meals the total counts for more.^1,3

Timing around medicines

Ask your pharmacist or doctor first

Protein can lower how much levodopa is absorbed. The carbidopa and levodopa label says levodopa competes with certain amino acids to cross the gut wall, so a high-protein diet may delay its absorption and reduce the amount that reaches the blood.⁶

On the medicine's label

If you take levodopa, ask your doctor or pharmacist how to fit protein around your doses rather than changing the timing yourself.⁶

Questions people ask

Should I drink a protein shake in the morning or at night?

Either works. Total daily protein mattered more than timing in the trials pooled so far. The one time singled out in studies is before bed, with 27.5 to 40 g of casein.^1,2

Is it better to take protein before or after a meal?

No study found for this page compared the two for muscle. The guidance is about the size of each serving and the spacing between servings, not their order around a meal.³

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Sources

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.