If you're battling a protein deficiency, your body might be trying to tell you. That’s why it’s a smart training move — and an overall wise health move — to be able to recognize signs of low-protein and address them properly.

Adults need around 0.36 grams of protein per pound of body weight per day, but many nutritionists feel that’s not enough, especially for athletes.

“Protein is the building block of DNA, and every single part of us has DNA,” Monica Auslander, a Miami-based dietitian and the founder of Essence Nutrition, says.

Related: 3 Surprising Science-Backed Reasons Spartans Should Eat More Protein

And if you’re physically active, you likely need to eat more protein.

“Nutritionally, protein is the fuel for thousands of metabolic functions in our body,” Auslander says. “Our cell systems require it to manufacture hormones, enzymes, bone, cartilage, skin, tissue, and blood.”

So, knowing the signs of low protein is crucial, so you can respond correctly when your body tells you it's time to consume more of the vital macronutrient. 

10 Common Signs of Low Protein

1. You Don’t See Noticeable Gym Gains

All of that time in the gym may be for nothing if you’re not getting enough protein, Jim White, a registered dietician nutritionist and owner of Jim White Fitness and Nutrition Studios, says. Why? Because when your body starts showing signs of low protein, it will break down muscle fiber to get what it needs. It doesn’t matter how many reps you do. Without protein, you won’t build brawn.

2. You Sputter Mid-Workout

“When your muscles don’t have fuel, neither do you,” Auslander says.

Plus, protein plays a critical role in how well your body absorbs other vital nutrients, like iron and calcium. When your nutrient tanks are low, your stamina suffers — another sign of low protein.

Related: These 5 Vitamin and Recovery Supplements Will Boost Your Energy

The best protein sources are real foods: dairy, meat, eggs, and the like. Or, you can add protein powder or collagen to your smoothies, oats, and even coffee.

3. You Feel Sick a Lot

If you’ve had to miss a few gym days because you’re under the weather, take a look at your diet.

“Protein plays a very important role in the immune system,” White says, adding that it constructs the cells that keep you healthy. “So if you’re not consuming enough, you may frequently fall ill.”

Related: 8 Ways to Avoid Getting Sick This Winter

To get more benefits from the protein you eat, add foods that contain leucine. Milk, cheese, beef, tuna, chicken, peanuts, soybeans, and eggs are all good sources and will quickly combat the signs of low protein.

4. You Battle Insomnia

Stress isn’t the only thing that can keep you awake at night. If your body thinks it’s starving, it wants you to eat, not sleep. Protein improves the feeling of post-meal satisfaction. Without that feeling, your body may have trouble settling into a deep and restorative resting state, Auslander says. That’s one reason you should consume protein at bedtime.

Related: 10 Ways to Stop Sabotaging Your Sleep Hygiene

5. Your Attitude Sucks

Have you been snapping at your significant other or some guy in your office? Irritability is one of the signs of low protein. By mitigating the effect of carbohydrates, slow-digesting protein helps keep your mood stable.

“If your diet doesn’t have enough protein to stop insulin spikes and dips, your personality will definitely be affected,” Auslander says.

6. You Have Too Many Injuries

When you don’t get enough protein, your body has a hard time absorbing calcium, and that can lead to decreased bone mineral density. Weaker bones increase the chances you’ll hurt yourself when you crank up the treadmill to sprinting speed.

Related: Don't Be Dumb. Deal With Your Injuries BEFORE Your Race.

7. You Heal Slowly

According to White, protein puts you back together. So if you exhibit signs of low protein and suffer a cut, bruise, or scrape, the injury may stick around longer if there isn’t enough tissue-building material present to build new cells and tissue.

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8. Your Scalp Is Showing

If you’re genetically prone to baldness, there’s almost nothing you can do to stop it. But for some of us, sudden hair loss could be a sign of a protein deficiency.

“Protein aids in your body’s ability to produce new cells, which means that without enough of it, you may experience thinning hair,” White says.

Related: 5 Reasons That Spartans Eat Whole Food-Fueled Meal Plans

And while we’re on the cosmetic stuff, weak nails and dry skin can also signal low protein intake.

9. You Crave Cookies

Carbs alone can’t satisfy you, Auslander says. You need protein to feel full, and to signal to your body that you’re supplying it with the food that it needs. If your brain is always in scavenger mode, you start to crave all of the bad-for-your-training stuff.

10. You Can’t Focus

Protein is literal food for thought; without it, the neurotransmitters in your brain can’t function properly. That means that you’ll have trouble concentrating, and you’ll probably be easily distracted, White says.

If you have any of these signs of low protein, look for ways to add more protein to your diet. With supermarket shelves full of protein powders, protein bars, and more, it shouldn’t be hard.