Should I use first morning urine for the collection?

No — OncuraKit recommends a mid-stream, mid-day urine collection rather than first morning urine. First morning urine is the most concentrated urine of the day and may contain higher concentrations of cellular debris, bacteria, and other contaminants from overnight bladder residence. While the Yenos normalization protocol compensates for concentration differences, a mid-stream collection from a partially full bladder (2–4 hours after your last urination) minimizes interference from contaminants and provides a good representation of circulating miRNA levels. Follow the detailed collection instructions included in your kit — they specify the recommended collection timing and mid-stream technique.