Anemia (anaemia or anæmia; from Greek: ἀναιμία, anaimia, meaning "Name means::lack of blood") is a blood condition where there is less than normal amounts of red blood cells in the blood, caused by various factors and conditions. It affects all ages and all races, but severity and type of anemia could depend on age and heredity.
If a person has mild anemia, sometimes there are no symptoms. Other times, if anemia is slow-developing, the body can adjust, and once again, not show any symptoms. Some small signs that anemia may be developing are fatigue, weakness, pale skin coloration, lightheadedness, insomnia, difficulty concentrating, and shortness of breath. In severe cases, life-threatening symptoms may occur, such as chest pain, heart attack, fainting, dizziness, and a rapid heart rate.  For specific causes of anemia, there are specific symptoms. For example, iron deficiency anemia can cause the sufferer to crave strange things such as paper, dirt, ice, etc. A sufferer of vitamin deficiency anemia might experience hallucinations, paranoia, or schizophrenia. 
There are hundreds of various causes for anemia, but three most common causes: anemia because of blood loss, decreased red blood cell production, and destruction of healthy red blood cells. 
This is a direct result of a significant drop in the amount of blood being circulated throughout the body. The average amount of blood in an adult body is around 5,000 to 6,000 ml. However, the human body can lose up to 500 ml without leaving damaging effects on the body. Any loss of over 1,000 ml could be life threatening. Anemia caused by loss of blood can sometimes go undetected. Regular bleeding is normal, such as menstrual bleeding for women, who on average lose 44 ml per monthly cycle, but this number could be much higher for heavy menstruation cycles.  Continual chronic blood loss can cause many health problems. Extreme blood loss could be from injury, intestinal bleeding, surgery, or problems relating to blood clotting. If blood loss anemia is suspected, but you can’t easily detect the reason for blood loss, there are a few tests doctors can give to find where bleeding is coming from.  With an insufficient amount of blood in the body, organs will have trouble functioning at their optimum level due to less oxygen and iron intake from red blood cells. 
Decreased Red Blood Cell Production
Sometimes, anemia can occur when bone marrow can’t make enough red blood cells, or makes them too slowly, to keep up with demands in the body. Exposure to radiation, chemicals, or some medications, can cause bone marrow to slow down erythrocyte production. Red blood cells only live for a few days in the blood stream, and eventually need to be replaced. That’s where bone marrow comes in, under ideal circumstances, and would make an equal amount of red blood cells to replace those that die off. 
Destruction of Existing Red Blood Cells
The breakdown of red blood cells prematurely is sometimes called hemolytic anemia. The cells can be destroyed in the blood vessels or other places in the body. In normal cases when destruction of red blood cells is quickened, bone marrow can adjust and simply produce erythrocytes more quickly, if needed. If red blood cells are being destroyed faster than bone marrow can produce replacement cells, anemia develops and is then called hemolytic anemia. About 5% of all people with anemia suffer specifically from hemolytic anemia. 
- Main Article: Sickle cell anemia
More than 70,000 Americans have sickle cell anemia, making it one of the most common types of anemia.  Sickle cell anemia is a very serious type of anemia where the usual doughnut or disc shaped red blood cells are produced in a very different shape, looking similar to the letter “C”. Normal red blood cells are able to move easily through blood vessels because of their shape and smooth roundness. Sickle cells are slightly sticky and often clump together in blood vessels, along with other cells, which blocks blood flow to limbs and organs of the body. Healthy red blood cells live for an average of 120 days, whereas sickle red blood cells can only survive 10 to 20 days. Bone marrow can’t keep up with the rate of production necessary, so anemia develops. Sickle cell anemia is an inherited condition that is passed on from parent to child. Children with sickle cell anemia grow at a much slower rate than other children their age, and often hit puberty much later than their peers as a result of sickle cell condition.
One reason the sickle cell DNA persists in the human population, despite being homozygous for it can be fatal, is that being heterozygous for the condition provides protection against malaria. Thus is has some use to those who live in areas prone to malarial infections.
The most common, and easily curable, type of anemia is iron deficiency anemia. This kind of anemia occurs when there is both a lack in red blood cells and iron attached to the hemoglobin in those blood cells. People with iron deficiency anemia often don’t even know they have it, because symptoms are not always bold, like other forms of anemia. Symptoms include fatigue, cold hands and feet, loss of appetite and irritability. One possible reason for a lack of iron is the inability to absorb iron through the intestine walls. Another is a lack of iron in a person’s diet, which can easily be solved by eating more iron-rich foods such as dark leafy green vegetables, eggs, meat, dairy products and iron-fortified foods. Possible problems related to iron deficiency anemia are stunted growth, heart problems, and premature births for pregnant anemic mothers. 
Vitamin deficiency anemia is just as the name implies: a lack of a certain vitamin in the body. For this specific type of anemia, vitamin B12 is to blame. Without this essential vitamin, red blood cells become enlarged and abnormal. The cause is quite simply a lack of vitamin B12 in a person’s diet or inability of the intestine to absorb the vitamin into its walls. Signs of a vitamin deficiency are fatigue, tingling sensations on hands and feet, and weakness. Treatment for this type of anemia is quite simple, and works well in most cases: take vitamin B12 supplements to replace however much is not being absorbed into the body. It can be taken as a nasal spray, injection, or tablet form for oral administration. 
Treatment for anemia depends a lot on which type of anemia the patient suffers from. For iron deficiencies, taking a liquid or pill iron supplement is sometimes enough. In some very serious cases, hormone injections, surgery, or blood transfusions could be necessary. For vitamin deficient patients, getting vitamin B12 injections monthly is a lifelong commitment to keep anemia from returning.  If anemia is caused by blood loss, blood transfusions, oxygen, iron supplements can help, but the main problem, which is blood loss, must be dealt with first to make sure it is even possible to return back to complete health. 
- Understanding Anemia Robert J. Byrg, WebMD, December 14, 2008.
- Anemia Causes, Symptoms, Diagnosis and Treatments Saimak T. Nabili, eMedicineHealth, December 9, 2008.
- Blood Loss Anemia Author Unknown, Innvista, Date Unknown.
- Anemia FAQs Multiple Authors, National Anemia Action Council, Date Unknown.
- Anemia Robin E. Miller, Kids Health, January 2006.
- Aplastic Anemia C.F. LeMaistre and Anthony S. Stein, National Marrow Donor Program, Date Unknown.
- Hemolytic Anemia Paul Schick, eMedicine, January 29, 2007.
- Sickle Cell Anemia James Fahner, Teens Health, June 2007.
- Anemia Disease by GenericLook.com
- Sickle Cell Anemia Author Unknown, Heart Lung and Blood Institute, August 2008.
- Iron Deficiency Anemia Mayo Clinic staff, MayoClinic, March 24, 2009.
- Vitamin Deficiency Anemia Alan E. Lichtin, Merck, June 2008.
- Symptoms, Treatment and Prevention Author Unknown, USA Today, Date Unknown.