I've always assumed prankster-loving baristas might substitute decaf coffee for the real thing. I'm sure there are those out there who would not think twice about slipping some caffeine to an unsuspecting customer. Whether accidentally or on purpose, for some, this unexpected addition of caffeine could be a serious health threat--at least serious enough to warrant caution.
Those who have high blood pressure or a heart condition should probably be avoiding caffeine. However, as many people tend to do, the doctor's advice goes out the window when in the real world of cafes, restaurants, and soda pop machines. For people who simply must monitor their caffeine intake, there is help in the form of D+caf Caffeine Test Strips.
The test strips work quickly and easily: take a small sample from any suspicious beverage and apply it to the strip; after about a minute, the amount of caffeine present in the sample is indicated in a simple-to-read format. If the dark line on the "D" side is filled, you've got decaf, while the "C" side is reserved for --you guessed it--caffeine. While all decaffeinated beverages contain some amount of the drug, if it's under 20 milligrams per 6 ounce serving, the D+caf strips consider the beverage decaffeinated, and you can thank your friendly barista with a visit to the tip jar.