Can I mail my sample on a Friday or over a weekend?

We strongly recommend NOT mailing your specimen on a Friday or on a day that precedes a holiday. Pre-paid overnight shipping operates Monday–Friday for standard overnight delivery. A specimen dropped at USPS or FedEx on a Friday evening is unlikely to be picked up and delivered until Monday — a 72-hour window that pushes the boundaries of specimen stability. Similarly, holiday weekends extend delivery times. The safest collection days are Monday through Thursday. If you collect on a Friday, keep the specimen sealed and refrigerated (not frozen) and mail it the following Monday morning. However, collecting fresh and mailing immediately Monday–Thursday is always the recommended approach.