One (rare) unit of heat is the pound calorie (lb-cal), defined as the amount of heat required to raise the temperature of one pound of water by one degree Celsius. On this scale the specific heat of water would be 1 lb-cal/(Kâlb).
Usually, menstrual bleeding lasts about 4 to 5 days and the amount of blood lost is small (2 to 3 tablespoons). However, women who have menorrhagia usually bleed for more than 7 days and lose twice as much blood. If you have bleeding that lasts longer than 7 days per period, or is so heavy that you have to change your pad or tampon nearly every hour, you need to talk with your doctor.
Shortages of all types of blood occur during the summer and winter holidays. If all blood donors gave 2 to 4 times a year, it would help prevent blood shortages. If you began donating blood at age 17 and donated every 56 days until you reached 76, you would have donated 48 gallons of blood. About three gallons of blood supports the entire nation's blood needs for one minute.