Serum iron measures the iron circulating in your blood. Learn what your level means and how it relates to your overall iron status.
Serum iron measures the amount of iron circulating in your bloodstream, bound to a transport protein called transferrin. This is the iron that's immediately available for your body to use.
Think of serum iron as cash in your wallet — it's what you have on hand right now. Ferritin, by contrast, is like your savings account — your long-term reserves.
According to MedlinePlus, serum iron fluctuates significantly throughout the day (highest in the morning) and after meals containing iron. For this reason, it's usually interpreted alongside other iron markers.
Healthy circulating iron levels
Reduced iron availability, may indicate deficiency
Significantly depleted, likely iron deficiency
May indicate iron overload or recent iron intake
Select your iron value for a detailed explanation of what it means and what to do next.
Serum iron must be interpreted with other markers. According to StatPearls, here's how to read the patterns:
| Condition | Serum Iron | TIBC | Ferritin | TSAT |
|---|---|---|---|---|
| Iron Deficiency | Low | High | Low | <20% |
| Chronic Disease | Low | Low/Normal | Normal/High | Low/Normal |
| Hemochromatosis | High | Low | High | >50% |
| Normal | Normal | Normal | Normal | 20-50% |
Serum iron is one of the most variable blood tests. Your level can change significantly based on:
Blood loss, poor dietary intake, or malabsorption. Ferritin will also be low, and TIBC will be high. This is the most common cause.
Inflammation from infection, autoimmune disease, or cancer causes iron sequestration. Ferritin may be normal/high, TIBC is low.
Surgery, trauma, heavy menstruation, or GI bleeding can acutely deplete circulating iron.
Simply testing in the afternoon can show "low" iron. Retest in the morning fasting if results are borderline.
Genetic disorder causing iron overload. Serum iron, ferritin, and transferrin saturation are all elevated. Requires treatment.
Iron supplements or iron-rich meal within 24 hours can spike serum iron. Retest fasting.
Damaged liver releases stored iron. Hepatitis, cirrhosis, and fatty liver can elevate serum iron.
Red blood cells breaking down release iron into circulation. Associated with elevated LDH and bilirubin.
Upload your lab reports and see iron, ferritin, and TIBC trends together. Know if your treatment is working.
Start Tracking Free