Protein needs vary from one athlete to another, so it can be hard to know if you’re getting enough of this macronutrient. If you’re spending most of your gym time in the weight room, your protein needs will tip to the higher end of the spectrum. But knowing exactly how much protein is enough can be tricky.

Scientists say that following certain recommended guidelines isn’t necessarily the way to go.

“There is a good rationale for recommending to athletes protein intakes that are higher than the RDA,” say scientists who published a paper in the Journal of Sports Sciences. The authors recommend an intake of protein 1.3g–1.8g per kilogram per day to maximize muscle protein synthesis. They add that consuming more protein (1.8g–2g per kilogram of body weight per day) during times of intense training or calorie restriction may be helpful as well.

But what happens if your daily protein intake falls short? These are some of the most common signs that you’re not getting enough protein.