Nadir timing influences laboratory monitoring during chemotherapy by guiding the timing of which test?

• A. CBCs are never checked.
• B. CBCs are often checked around the expected nadir to assess risk of infection and bleeding and to guide supportive care timing.
• C. Only chemistry panels are checked.
• D. Blood glucose is the primary concern.

Answer: (B)

Nadir timing helps you time monitoring to the period when bone marrow suppression is greatest. After chemotherapy, the white blood cells (especially neutrophils) and platelets can drop to their lowest point—the nadir—at a predictable time, which is when infection and bleeding risk are highest. The complete blood count is the most informative test at this window because it directly shows the absolute neutrophil count and platelet count, telling you who is at risk and guiding whether to start supportive care, give growth factors, or delay the next cycle.

Chemistry panels and glucose tests assess organ function and metabolism, not the marrow’s suppression, so they don’t provide the critical information about infection or bleeding risk that nadir monitoring targets. Although nadir timing can vary by regimen, many protocols schedule CBCs around the expected nadir to make timely decisions for safety and treatment planning.