Paddy goes into the chemist's shop, reaches into his pocket and takes out a teaspoon and a small bottle. He pours some liquid into the teaspoon and offers it to the chemist.
"Could you taste this please?"
The chemist takes the teaspoon, puts it in his mouth, swills the liquid around and swallows it.
"Does it taste sweet?" says Paddy
"No, not at all" says the chemist
"Good" says Paddy "the doctor told me to come here and get my urine tested for sugar."