United Blood Services has issued an appeal for donors with rare Rh negative blood types, especially type O-Negative and type A-Negative.

Demand is very high for those blood types, while the number of people who have those types is very low. The blood center is especially seeking new donors who perhaps don’t know their blood type. Those who have never donated are especially encouraged to come forward.

Type O-Negative blood is found in just 7 percent of the population. Known as the “universal donor,” this blood type can be transfused to anyone. In emergency and trauma situations, when there is little time to “type” a patient’s blood, O-Negative blood can be immediately transfused to the patient, making this blood type highly needed. Patients often need multiple units — in some cases hundreds of units.

Likewise, a mere 6 percent of the population has type A-Negative blood. As it can be safely transfused to any patient with type A or AB blood (both positive and negative) it, too, is often needed. Again, multiple units may be needed by any one patient.

Donors are needed each day to maintain an adequate supply, and current usage for type O-Negative and A-Negative is running high. Blood is also perishable and has a short shelf life, making daily donations particularly important. Unlike other products, blood cannot be manufactured.

Donations may be made at the UBS Center in Santa Barbara at 902 Laguna St., at the corner of Cañon Perdido. Appointments are appreciated, but not necessary. Walk-ins are welcome and will be honored as the appointment schedule allows.

Center hours are 10 a.m. to 6 p.m. Monday and Tuesday, 10 a.m. to 7 p.m. Wednesday and Thursday, and 8 a.m. to 3 p.m. Friday.

People may donate blood if they are older than age 16, weigh at least 110 pounds and are in good health. Additional height/weight requirements apply to donors age 22 or younger.

Donors are asked to make an appointment by contacting United Blood Services at 800.715.3699 or online at www.Blood4Life.org. Just click on “Donate Blood” and type in a ZIP code to find a list of nearby drives.

— Scott Edward is the donor recruitment director for United Blood Services.