Do miRNA levels fluctuate day-to-day or seasonally?

Short-term biological variation in miRNA levels is a recognized phenomenon — levels can fluctuate within an individual based on hydration status, recent acute illness, stress, and other factors. The Yenos HL normalization accounts for hydration variation by expressing results as a ratio of cancer miRNA to total RNA. However, acute illness (fever, infection) can transiently elevate inflammatory miRNAs including miR-21. For this reason, we recommend collecting your sample when you are in normal, everyday health — not during or immediately after a significant acute illness. Day-to-day variation in healthy individuals is not expected to push levels above the 1.5× HL threshold, given that healthy individuals in Yenos studies consistently scored around 1.04× HL with relatively low variability (RSD 0.17).