Large Unstained Cells (%)
Large unstained cells, or LUCs, is an analyzer category for larger white cells that don't take up a particular stain the way typical cells do. This figure shows what percentage of your white cells fall into that group, which can include activated lymphocytes and other atypical cells.
This is an automated flag rather than a specific cell type, so it mainly signals that some cells look unusual and may deserve a closer look. It can prompt a technologist to review the blood smear under a microscope. On its own it is a screening cue, not a diagnosis.
A higher LUC percentage can appear when the immune system is activated, such as during some viral infections, or when atypical cells are present. Because it is a non-specific analyzer category, an elevated value usually leads to a manual smear review rather than a conclusion. Your clinician will interpret it with the rest of your blood picture.
A low or zero LUC percentage is common and generally not a concern.
This value is analyzer-specific and not reported by all labs; use your report's range and let your clinician decide whether a smear review is warranted.
Sources
Educational context only, not medical advice or a diagnosis. Reference ranges vary by lab, age and sex; always discuss your results with a clinician.