When a person is anemic, they are low in red blood cells. Red blood cells carry oxygen in the blood so when a person does not have enough, the body may not be getting the oxygen it needs.
16 Symptoms of Anemia (Iron Deficiency)
When you are anemic, you may not have any symptoms. If you do have symptoms of anemia, tiredness and weakness are common. Other symptoms you may have when you are anemic include:
- Headache
- Irritability
- Shortness of breath/trouble breathing
- Rapid heartbeat
- Difficulty exercising
- Chest pain
- Sore tongue
- Brittle nails
- Muscle pain
- Restless legs syndrome
- Abnormal cravings for non-food items, such as clay or dirt, paper products, or cornstarch (pica)
- Abnormal craving to eat ice (pagophagia)
- Pale skin or pale color in the tissue that lines the inside of the eyelids
- Reddish or brown urine (autoimmune hemolytic anemia)
- More frequent infections (aplastic anemia)
- More bruising or bleeding than normal (aplastic anemia)
What Causes Anemia?
There are different types of anemia. Causes of anemia depend on the type and may include:
- Iron deficiency anemia
- Inadequate dietary iron intake
- Loss of large amounts of blood
- Decreased iron absorption from food
- Pregnancy and the postpartum period
- Anemia of inflammation or anemia of chronic disease
- Autoimmune hemolytic anemia
- Is a result of problems with the body's immune system in which the immune system mistakenly attacks and destroys red blood cells
- The cause is frequently not known but may be related to:
- Autoimmune diseases such as lupus
- Infections such as pneumonia and mononucleosis (“mono”)
- Some types of cancer, including chronic lymphocytic leukemia (CLL), multiple myeloma, and lymphoma
- Use of certain medicines, including some antibiotics
- Aplastic anemia
How Is Anemia Diagnosed?
Anemia is diagnosed with a medical history and physical examination, along with blood tests.
Blood tests used to diagnose anemia include:
- Complete blood count (CBC)
- Serum iron
- Ferritin
- Total iron binding capacity (TIBC or transferrin)
- Transferrin saturation (TSAT)
A bone marrow biopsy may also be performed to help diagnose aplastic anemia.
What Is the Treatment for Anemia?
Treatment for anemia depends on the type.
For iron deficiency anemia, the cause of the iron deficiency must first be determined. If low iron is due to blood loss, such as from stomach ulcers or bowel problems, those problems need to be treated.
People with iron deficiency anemia need additional iron and eating iron-rich foods is not enough. Iron supplementation may be given:
- Orally as pills or liquid
- Intravenously
If iron deficiency anemia is severe, a blood transfusion may be needed.
For some cases of anemia of inflammation, erythropoietin or erythropoiesis-stimulating agents (ESAs) that help the body produce more red blood cells may be used.
Autoimmune hemolytic anemia is treated with:
- Treating any underlying condition
- Medications
- Prednisone
- Cyclophosphamide (Cytoxan) or rituximab (Rituxan) if prednisone does not work
- Blood transfusions
- Spleen removal (splenectomy)
Treatment for aplastic anemia depends on the cause and may include:
- Stopping medicines that caused the problem
- Don’t stop taking a prescribed medication without talking to your doctor first
- Medications
- Antibiotics
- Antivirals
- Immunosuppressive medicines
- Transfusion of red blood cells or platelets
- Avoiding toxic chemicals
- Bone marrow transplant (stem cell transplant)
From 
Healthy Resources
https://www.uptodate.com/contents/anemia-caused-by-low-iron-in-adults-beyond-the-basics?search=low%20hemoglobin&topicRef=15339&source=see_link
https://www.uptodate.com/contents/anemia-of-inflammation-the-basics?search=low%20hemoglobin&source=search_result&selectedTitle=1~150&usage_type=default&display_rank=1
https://www.uptodate.com/contents/autoimmune-hemolytic-anemia-the-basics?search=low%20hemoglobin&source=search_result&selectedTitle=2~150&usage_type=default&display_rank=2
https://www.uptodate.com/contents/aplastic-anemia-the-basics?search=low%20hemoglobin&source=search_result&selectedTitle=3~150&usage_type=default&display_rank=3