Unsaturated Iron Binding Capacity
Iron Studies marker
UIBC
Unsaturated Iron Binding Capacity
The reserve iron-binding capacity of transferrin: the portion not currently carrying iron. UIBC plus serum iron equals the total iron binding capacity (TIBC). It rises in iron deficiency and falls in iron overload or inflammation.
PED Notes
UIBC is directly tied to the iron paradox on TRT and AAS. Testosterone and other androgens stimulate erythropoiesis, and the surge in red-cell production consumes iron stores, so a bodybuilder can be building red cells (high haemoglobin and haematocrit) while running low on iron. As iron stores fall, the body upregulates transferrin, so UIBC (and TIBC) rise while serum iron and ferritin drop. Regular blood donation to manage high haematocrit accelerates this, each donation removing roughly 250mg of iron. Read UIBC together with ferritin, serum iron, and transferrin saturation rather than alone. No PED sets a different healthy target, so the bodybuilder range equals the standard range.
When high
When elevated (>346 ug/dL -- suggests iron deficiency):
- A high UIBC means transferrin has plenty of spare binding capacity, typical of iron deficiency, where the body ramps up transferrin to capture more iron.
- What to do:
- Confirm with ferritin (low), serum iron (low), and transferrin saturation (low); the combination of high UIBC + low ferritin + low saturation confirms true iron deficiency, common in AAS users who donate blood.
- Supplement: iron bisglycinate 25-50mg elemental iron/day, taken on an empty stomach with vitamin C to aid absorption; avoid coffee, tea, and calcium within 2 hours.
- If you donate blood to control haematocrit, replace iron between donations and target ferritin >50 ug/L before the next donation.
- Recheck iron studies 6-8 weeks after starting supplementation; persistent deficiency despite supplements warrants investigation for blood loss.
When low
When low (<112 ug/dL -- suggests iron overload or inflammation):
- A low UIBC means little spare binding capacity. It occurs when iron stores are high (iron overload, haemochromatosis) or when inflammation lowers transferrin, and can also reflect reduced transferrin synthesis in liver disease.
- What to do:
- Interpret with ferritin and transferrin saturation: low UIBC with high ferritin and high saturation points to iron overload; investigate hereditary haemochromatosis (HFE testing) and avoid iron supplements.
- Low UIBC with high ferritin but low serum iron suggests anaemia of inflammation, where ferritin is falsely elevated as an acute-phase reactant; look for and treat the inflammatory source.
- In oral-AAS users, consider liver-related reductions in transferrin synthesis if liver enzymes are abnormal.
History Chart
Reading History
Frequently Asked Questions
Reference Ranges
Standard Range
VitalMetrics Range