TikTok is a fantastic place to discover new things to worry about, or new ways to worry about old things. The latest is the “dehydration check,” in which you pinch the skin on your knuckle. If the skin stays wrinkled for a few seconds, that’s (supposedly) your sign to grab a glass of water.
Folks, there is no epidemic of dehydration that we can accidentally fall prey to. If your body needs a glass of water, you will feel a sensation known as thirst. Amazing, right? No dehydration check needed.
There are situations where you might want to test if somebody is dehydrated, especially if you are caring for an older person who might not feel thirst signals as reliably, or a person who may have trouble getting themselves a drink or communicating that they need one. The medical literature on assessing dehydration usually focuses on elderly folks, children, and people with other medical issues. Not healthyish adults who are bored and filling the void by scrolling through TikTok.
The TikTokers are doing it wrong, anyway
So is the pinch-your-skin test for real? Sort of. Medical professionals will talk about skin turgor as one of the signs of hydration. (Turgor means stiffness; good skin turgor means the skin will bounce back, and indicates that you are well hydrated.) For example, if a nurse wants to check whether a patient might be dehydrated, they might use this test.
Even so, this reference for nurses explains that the skin turgor test is only one of many ways to monitor a patient’s hydration status. It also explains a little something the TikTokers seem to have missed:
Assess skin turgor by gently pinching a fold of skin between your thumb and forefinger. The skin you select, such as below the clavicle or on the abdomen, sternum, or forearm, should feel resilient, move easily, and quickly return to its original position when released after a few seconds. If not, the patient may be dehydrated.
Don’t test skin turgor on the dorsal [back of the] hand or anywhere the skin seems loose or thin.
Go ahead, try pinching the skin of your forearm. Mine snaps right back, even though the skin on my knuckle takes a few seconds to return to normal after a pinch.
Lack of skin turgor, as measured by pinched skin on the forearm or abdomen staying tented, indicates moderate to severe dehydration, defined as 10% of your bodyweight or more. So if you are normally 68 kg, but managed to lose 6kg of water somehow, a proper skin turgor test will indicate that you are dehydrated. You will also feel like shit, and it will be no mystery whether or not you are dehydrated.
There are some more caveats to the skin turgor test, which don’t really matter for healthy TikTokers but which are worth noting if you’re curious about how all this works. A review of skin turgor testing on children has shown that it’s not very reliable, and a review on assessing dehydration in older adults points out that skin turgor is not a great measure, because our skin loses elasticity as we age.