A nurse is assisting in preparing an in-service program about preventing medication errors when transcribing a prescription. The nurse is using a dosage example of four tenths of a milligram. Which of the following transcription examples should the nurse use?

The correct answer is B: 0.4 mg. When transcribing a dosage of four tenths of a milligram, it should be written as 0.4 mg to ensure clarity and accuracy. Using 4.0 mg (Choice A) would imply 4 milligrams, which is significantly different. 4 mg (Choice C) would indicate 4 milligrams as well. 0.40 mg (Choice D) is not necessary as it adds unnecessary zeros after the decimal point, making it less clear. Therefore, B is the most accurate and appropriate transcription example for four tenths of a milligram.