Creatine is a compound of three naturally-occurring amino acids that’s stored in our muscles. It’s thought to help you get those gains at the gym and amp up your lean muscle mass, among other health benefits.

“Research on creatine has shown that it may help athletes to do more sprints or reps, which can lead to greater strength gains, muscle mass, and improved performance,” say Lyssie Lakatos, RDN, CDN, CFT and Tammy Lakatos Shames, RDN, CDN, CFT, The Nutrition Twins, founders of The 21-Day Body Reboot, noting that it’s believed to be especially useful in rapid recovery from high intensity exercise. “Research also shows it may help to prevent dehydration and cramping, as well as muscle, tendon, ligament, bone and nerve injuries,” they add.

How creatine helps you build muscle

As The Nutrition Twins put it, simply taking a supplement containing creatine won’t help you pack on more muscle. “However, taking creatine may help you see muscle gains when combined with an intense workout routine because it may help you complete more reps when you’re strength training or achieve a faster burst of speed when sprinting, both of which can help you build more muscle,” they say. “And since creatine can also help you recover more quickly from exercise, it means muscles can repair themselves more efficiently, making for speedier, easier muscle growth.”

Ahead, a look at six factors that influence how much creatine you store in your muscles, from meat intake to your age and gender. 

1. meat consumption

Meat can help you maximize your creatine stores and the benefits you reap from exercise, say The Nutrition Twins. So if you’re a vegan or vegetarian, you may be low on the substance.

“Since creatine is mostly found in food sources like red meat, seafood, and poultry, those with vegan and vegetarian diets typically have lower levels of creatine in their blood and muscle tissue,” explain The Nutrition Twins. “However, those with lower creatine stores to begin with, like vegetarians and vegans, usually reap more benefits from supplementation and see great improvements in lean muscle mass and exercise performance.”

Read More: 3 Health Benefits Of Creatine Besides Muscle Building 

2. seafood consumption

Like meat, seafood such as herring, salmon, cod, and tuna are foods that increase the body’s creatine stores. “They have a similar creatine content to meat,” offer The Nutrition Twins, noting that herring, in particular, is a great source of creatine: “[It] provides nearly double the amount of creatine you’ll find in beef, an especially helpful factor for people who don’t eat meat [looking] to maximize their creatine stores.”

One caveat worth noting when it comes to diet and creatine: “The average omnivores diet contains about one gram of creatine daily and about 20 percent of meat eaters are considered ‘non-responders’ and won’t get additional benefits from creatine supplementation because their stores are maximized from their diet,” say The Nutrition Twins. “However, for the other 80 percent of omnivores who would like additional benefits, getting about 3-5 grams of creatine daily from a supplement may step it up even more.”

3. How well your kidneys are performing

Creatine stores can also be a metric of kidney function. “One of your kidneys’ jobs is to filter creatine out of the blood and out of the body through urine,” explains Amy Gorin, MS, RDN, an inclusive plant-based dietitian and owner of Master the Media in Stamford, CT. “If your kidneys are not working properly, you may have a build-up of creatine in your body.” 

As Gorin notes, a doctor would do a blood or urine test to determine your creatine levels. “Higher levels may indicate altered kidney function, kidney damage, or kidney disease,” she says.

Read More: The Most Common Health Myths—Debunked

4. Your age and gender

How old you are your sex also play a role in creatine stores in your muscles. “How well your body is able to filter creatine from the blood and into the urine depends on both age and gender. For men ages 19 to 75, creatine clearance should be at 77 to 160 mL/min/BSA, according to the Mayo Clinic,” says Gorin. (This measurement refers to milliliters of creatine per minute per body surface area.) For women, normal creatine clearance is as follows:

• 18 to 29 years: 78 to 161 mL/min/BSA
• 30 to 39 years: 72 to 154 mL/min/BSA
• 40 to 49 years: 67 to 146 mL/min/BSA
• 50 to 59 years: 62 to 139 mL/min/BSA
• 60 to 72 years: 56- to 131 mL/min/BSA

5. Your muscle mass

The amount of creatine you can store depends on your total muscle mass. “You can produce about half of your daily creatine requirement naturally in your body, while the other half comes from food sources or supplements,” the Nutrition Twins say.

6. Supplement usage

Kim Yawitz, a registered dietitian and the owner of Two Six Fitness in St. Louis, Mo., explains that “with consistent use, creatine supplements can increase your intramuscular creatine stores by up to 30 percent.” According to Yawitz, “the quickest way to get more creatine in your muscles is to undergo a loading phase—which involves taking 5 grams of creatine monohydrate 4-5 times per day for one week.” She further notes that taking 3-5 grams of creatine per day after the loading phase can help you maintain your creatine stores. 

“You can also increase the amount of creatine in your muscles (albeit more slowly) by skipping straight to the maintenance dose of 3-5 grams per day,” Yawitz adds.