When certain heart medications are removed from rat muscle cells in a lab, the cells start taking in more creatine than before — like they're bouncing back stronger after a pause.

When scientists lowered the sodium levels around rat muscle cells, the cells absorbed much less creatine—showing that sodium is needed for creatine to get inside these muscle cells.

Your muscles use a special door called SLC6A8 to let creatine in, and this door only works when there’s more sodium outside the cell than inside — like a pump that needs salt to open.

Your muscles need sodium to pull in creatine, kind of like a battery-powered door — if the battery's dead or there's no sodium around, creatine can't get inside, even if you're drinking plenty of water.

In regular human red blood cells, about 40% of the creatine that gets inside does so using a special sodium-powered process, which means this system plays a big role in controlling how much creatine is inside the cells.

Even though blood cells from people with kidney disease let in more creatine, they don’t end up with more creatine inside — probably because something in their blood is blocking it from building up.