π©Έ Transferrin Saturation Calculator
How full are your iron transport proteins?
Transferrin saturation
For informational purposes only, not medical advice.
Transferrin saturation is serum iron divided by TIBC, times 100: the percentage of iron-transport protein currently carrying iron. Iron 60 with TIBC 300 gives 20 percent, the low edge of normal and the classic pattern of early iron deficiency. Below 20 percent, iron supply is falling short; above 50 percent, overload enters the differential.
Think of transferrin as delivery trucks and saturation as how full they are. Empty trucks mean the warehouse is bare; overloaded trucks mean iron is piling up where it should not. The percentage tells you which problem you have before the anemia even declares itself.
How to Use This Calculator
Enter serum iron and total iron-binding capacity from the same iron studies panel, both in mcg/dL. The tool divides and interprets.
Enter serum iron in mcg/dL from the iron panel.
Enter TIBC in mcg/dL from the same draw.
Read the saturation percentage and the interpretation band. Morning fasting samples are most consistent.
The Formula
TIBC measures all the seats on the trucks; serum iron measures the occupied seats. In iron deficiency the body makes more trucks (TIBC rises) while iron falls, so saturation drops from both directions, which is why it is more sensitive than either number alone. In overload, iron floods the system and saturation climbs while TIBC stays flat or falls.
Ferritin, the storage protein, completes the picture: low saturation with low ferritin is iron deficiency; low saturation with high ferritin suggests inflammation blocking iron use, the anemia of chronic disease. Never read saturation without ferritin when the answer matters.
Worked Example
Serum iron 60 mcg/dL, TIBC 300 mcg/dL: 60 divided by 300 is 0.20, times 100 gives 20 percent, right at the deficiency threshold. With a ferritin of 12 ng/mL this is straightforward iron deficiency; with a ferritin of 400 it would point at inflammation instead.
Contrast overload: iron 220, TIBC 280 gives 79 percent saturation, the pattern of hemochromatosis until proven otherwise. Same formula, opposite end of the spectrum, completely different workup. The percentage alone cannot name the disease, but it aims the investigation.
Reading Your Result
| Saturation | Meaning |
|---|---|
| Under 20% | Low. Iron deficiency likely; check ferritin and find the source of loss. |
| 20 to 50% | Normal iron supply. |
| Over 50% | High. Consider hemochromatosis or other overload; needs evaluation. |
My take: saturation is the best single iron number for screening, but ferritin is the best for confirming deficiency. Order and read them as a pair, and remember that inflammation raises ferritin while lowering saturation, the combination that confuses everyone once.
Limits
Serum iron swings through the day, highest in the morning, and recent iron pills or infusions distort it; TIBC falls in malnutrition and liver disease independent of iron. Pregnancy and oral contraceptives raise TIBC physiologically. The percentage is a snapshot of transport, not of stores, which is ferritin's job.
Related Tools
Iron status affects energy and performance: the BMI calculator frames nutrition status, the protein intake calculator covers dietary building blocks, and the blood pressure checker tracks circulation.
For informational purposes only, not medical advice. Consult a healthcare professional.
Frequently Asked Questions
What is transferrin saturation?
Serum iron divided by total iron-binding capacity, times 100. It shows what percentage of the blood's iron-transport protein is carrying iron: under 20% suggests deficiency, 20-50% is normal, over 50% raises overload concern.
How do you calculate iron saturation?
Divide serum iron by TIBC and multiply by 100, with both in the same units (mcg/dL). Iron 60 and TIBC 300 give 20% saturation.
What does low transferrin saturation mean?
Iron supply is insufficient for needs, most often iron deficiency from blood loss, poor intake, or malabsorption. Confirm with ferritin and investigate the source, especially GI loss in adults.
What does high transferrin saturation mean?
Possible iron overload, classically hereditary hemochromatosis. Persistent elevation above 50-55% warrants evaluation with ferritin, and possibly genetic testing, since untreated overload damages liver, heart, and pancreas.
What is the difference between saturation and ferritin?
Saturation reflects iron in transit right now; ferritin reflects stored iron. Deficiency usually lowers both, while inflammation lowers saturation but raises ferritin. Read them together.
Should iron studies be fasting?
Morning fasting samples are most consistent because serum iron has a diurnal rhythm, peaking in the morning. Non-fasting values are still usable but harder to compare across draws.
Can inflammation affect transferrin saturation?
Yes. Inflammation raises hepcidin, which traps iron in stores: saturation falls while ferritin rises. This anemia of chronic disease mimics deficiency on saturation alone, which is why ferritin and CRP help sort it out.
Does pregnancy change iron studies?
Pregnancy raises TIBC and expands plasma volume, lowering saturation physiologically while iron needs soar. Iron deficiency is common in pregnancy and guidelines support routine screening.
What TIBC patterns matter?
High TIBC with low iron is classic deficiency (more trucks, less cargo). Low TIBC with high saturation suggests overload or chronic disease. TIBC alone is rarely interpreted without the iron value.
Who should evaluate abnormal iron studies?
Your clinician, who will pair them with ferritin, blood counts, and history. Persistent high saturation especially needs follow-up, since early hemochromatosis is very treatable and late is not.