Mass General Hospital Blood Draw in Chelsea is open to Mass General Brigham patients with an order from their Mass General Brigham provider. No appointment is necessary for blood draw services. Hours are Monday through Thursday from 8:00 a.m. to 7:00 p.m., Friday from 8:00 a.m. to 5:00 p.m., and Saturday from 8:00 a.m. to 3:30 p.m. Closed on holidays.