A High TIBC with a Low Ferritin
This is the complete signature of absolute iron deficiency, with all three iron numbers agreeing. Stores are empty, supply is short, and the liver has responded by building more transport capacity than it can fill. Because the panel is unambiguous, the useful question is not what it shows but where the iron went.
The pattern on your report
- TIBC High · moderate Key
- Ferritin Low · marked Key
- Transferrin saturation Low · moderate Key
- CRP Normal Key
Printed as: CRP in mg/Lor mg/dL— A normal value here is what allows the ferritin to be read at face value.Ferritin in ug/Lor ng/mLTIBC in umol/Lor ug/dL— 60 umol/L is about 336 ug/dL. Reports giving transferrin in g/L are measuring a related but separate thing and cannot be compared against a TIBC range.Transferrin saturation in %
Why the numbers look like this
Transferrin is the protein that carries iron through the blood, and the liver produces more of it when iron is scarce. TIBC measures the total capacity of that transport system, so it rises as an adaptive response to shortage.
That direction is what makes it diagnostic. In inflammation, transferrin production falls with other liver export proteins, so the TIBC drops. Two conditions both give a low saturation, and the TIBC moves opposite ways in them, which is why it belongs on any iron panel worth ordering.
So the three numbers here describe one coherent state: an empty warehouse, an under-filled fleet, and more lorries built in response. Nothing about the panel is ambiguous, which shifts the question entirely to the cause.
Not being flagged is not the same as normal
TIBC upper limits sit near 80 umol/L and vary by laboratory and assay, and some reports give transferrin in g/L instead, which is a related but different measurement that cannot be compared against a TIBC range. Ferritin has the more consequential threshold problem: WHO defines depleted stores below 15 ug/L while UK gastroenterology practice diagnoses iron deficiency nearer 30, and laboratory flags often start lower still. A ferritin of 20 with this TIBC is iron deficiency whichever line is used.
What else on the report can hide this
The panel has answered its question, so nothing further about iron status is needed. What is needed is a source, and age and sex determine how hard to look. In a menstruating person heavy periods explain most of it and no search for another source is usually required. In a man or a postmenopausal woman there is no physiological route for iron to leave, which makes gastrointestinal investigation the standard next step rather than an optional extra.
Celiac serology belongs alongside, with a total IgA, since impaired absorption is the commonest non-bleeding cause and is easily missed.
Think, too, about where you live and have lived. Hookworm is a leading cause of iron deficiency in endemic regions, and it is diagnosed by asking and by a stool test, not by any of the numbers on this panel.
What usually causes it
Listed from most to least common — not from most to least serious.
- Very common
Menstrual blood loss — in menstruating people
The leading cause in this group by a wide margin, and it usually needs no search for another source. Heavy or prolonged periods, clots, or flooding through protection.
- Very common
Low dietary iron or poor bioavailability
Little red meat, a vegetarian or vegan diet, or tea and coffee taken with meals. Plant iron absorbs several times less efficiently.
- Common
Bleeding in the gut
The cause that must be excluded in men and postmenopausal women, because no physiological route exists in either group. Frequently silent.
- Common
Celiac disease or another absorption problem
H. pylori, long-term acid-suppressing drugs, or previous stomach surgery. Suspect it when intake looks adequate and no bleeding is found.
- Common
Pregnancy and breastfeeding — in pregnancy and the year after
Demand climbs steeply from the second trimester. Expected, and still needing treatment rather than observation.
- Common
Hookworm or other intestinal parasites — in people living in or returning from endemic regions
A leading cause in endemic regions and easily overlooked where it is rare. Residence and travel history, then a stool test.
- Common
Frequent blood donation
Each donation removes a substantial amount of iron, and stores can stay flat while hemoglobin recovers enough to pass screening.
- Uncommon
Long-term aspirin or anti-inflammatory use
Causes slow gastric blood loss that produces no symptoms until the count falls.
- Uncommon
A tumor of the stomach or bowel
The reason unexplained iron deficiency in an older adult is investigated rather than simply treated.
What is usually checked next
- Celiac serology with a total IgA The commonest absorptive cause. The total IgA is required, because IgA deficiency makes the celiac test read falsely negative.
- Endoscopy and colonoscopy where indicated by age and sex Standard in men and postmenopausal women, because there is no physiological route for iron loss in either.
- A travel and residence history, with stool testing Finds the parasitic causes, which no blood test on this panel will show.
- A menstrual history, where relevant Explains most cases in menstruating people, and it is worth treating the loss as well as the iron.
- Repeat ferritin after three months of treatment Hemoglobin corrects long before stores refill, so stopping when the count normalizes leaves the tank empty.
When to seek care sooner
- Emergency Vomiting blood, or black tarry stools
- Emergency Chest pain, breathlessness at rest, or fainting
- Same day Visible blood in the stool
- Soon Unintentional weight loss, or a change in bowel habit lasting several weeks
- Soon Iron deficiency in a man or a postmenopausal woman with no source found
- Soon Difficulty swallowing
Questions worth bringing to your appointment
- Given my age and sex, do we need to look for a source of blood loss?
- Should I be screened for celiac disease, with a total IgA?
- Is a stool test worth doing given where I have lived or traveled?
- How long should treatment continue after my hemoglobin recovers?
- If my periods are the cause, is that worth treating in its own right?