Unsaturated iron-binding capacity (UIBC) is a blood test most frequently used along with a serum iron test and a total iron-binding capacity test (TIBC) to evaluate people suspected of having either iron deficiency or iron overload.
UIBC is used for calculation of TIBC: TIBC [µg/dL] = UIBC [µg/dL] + Iron [µg/dL]
Iron moves through the blood attached to a protein called transferrin. Your body makes transferrin in relationship to your need for iron. When iron stores are low, transferrin levels increase, while transferrin is low when there is too much iron. Usually about one third of the transferrin is being used to transport iron. Because of this, your blood serum has considerable extra iron-binding capacity, which is the UIBC. The TIBC is the total iron binding capacity. It equals UIBC plus the serum iron measurement. Some laboratories measure UIBC, some measure TIBC, and some measure transferrin. This test helps your doctor know how well that protein can carry iron in the blood. One or more tests may be ordered when there are signs of anemia, especially when a comprehensive blood count is performed and shows red blood cells that are microcytic and hypochromic and the hemoglobin and hematocrit levels are low.
The most common symptoms of anemia include:
- Chronic fatigue / tiredness
- Pale skin
When a healthcare professional suspects that a person may have iron overload or when a person has a family history of hemochromatosis then iron, UIBC, and TIBC may be ordered along with a ferritin test.
Symptoms of iron overload will vary from person to person and tend to worsen over time; they may include:
- Join pain
- Fatigue, weakness
- Weight loss
- Lack of energy
- Abdominal pain
- Loss of sex drive
- Loss of hair
- Heart problems
A low TIBC may occur if someone has:
- Certain types of anemia
- Liver disease
- Kidney diseases like nephrotic syndrome
- TIBC is usually higher-than-normal when the body's iron stores are low.
- A high TIBC usually indicates iron deficiency anemia or late pregnancy.
- Oral contraceptives may also cause TIBC to rise.
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