“Spoon dosing has been identified as 1 of the 3 major causes of dosing errors and pediatric poisonings,” authors of the study wrote. “Most persons still use spoons when pouring medicine for themselves and their families.”

Nearly 200 university students were asked to measure what they perceived to be equal amounts of cold medicine into three different spoons—a standard teaspoon, a medium-sized spoon, and a larger spoon.

“We first gave them a full bottle of cold medicine and a teaspoon and asked them to pour exactly 1 teaspoon (5 mL),” authors of the study explain. “Next, we asked participants to pour the same 5-mL dose into each of the remaining 2 spoons in a randomized order.”

Standard dosage for most cold medicines is usually between 2 teaspoons and 2 tablespoons. Although most participants were confident that they’d measured accurately, they measured 8.4 percent (.42 mL) too little when using the medium-sized spoon, and 11.6 percent (.58 mL) too much when using the large spoon.

Although that may not seem like much for per dose, a little change in medicine can make a lot of difference. According to study leader Dr. Brian Wansink of the Cornell Food and Brand Lab, this can add up to the point of ineffectiveness or even danger.

They also point out that this could reach farther than the kitchen at home. Even the most practiced nurse or Dr. Mom could be measuring incorrectly when using spoons because the size of the spoon makes the same amount appear differently.

“Simply put, we cannot always trust our ability to estimate amounts," co–author, Dr. Koert van Ittersum, Assistant Professor of Marketing at Georgia Tech, said in a press release. "In some cases it may not be important, but when it comes to the health of you or your child, it is vital to make an accurate measurement."