Wednesday, December 3, 2008 12:00 AM

(HealthDay News) -- Anemia occurs either when the blood is deficient in red blood cells, or it lacks enough of a protein called hemoglobin.

Some forms of anemia can be life-threatening if not diagnosed and treated, the U.S. Department of Health and Human Services says.

Here's the agency's list of warning signs that you may be anemic:

Feeling tired and weak.Experiencing paleness, dizziness, headache or shortness of breath.Having a lower than normal body temperature.Having cold or numb hands and feet.Having pains in your chest, or a very fast or abnormal heartbeat.Feeling irritable.Doing poorly at work or school.