Ferritin: the number that gets called normal at 15
Your ferritin came back at 15 and the note said normal. You are tired in a way that sleep does not fix, your hair is thinning, you get breathless on the stairs, and your legs will not settle at night. You were told your iron is fine. It is not fine. It is inside a range that was drawn in the wrong place, and the people who write the guidelines have started to say so.
I see this number more than almost any other in the folders women bring me. I want to explain what ferritin is, why the range is where it is, why women in their forties run low without knowing it, and what to ask for so you can stop being told you are fine.
What ferritin actually measures
Ferritin is the protein your body stores iron in. A blood ferritin is a rough read of how much iron you have in the bank. Hemoglobin, the number on the blood count, is the iron that has already been spent on red cells. You can have a normal hemoglobin and an empty bank, and that is exactly the pattern most women I see are in. It has a name, iron deficiency without anemia, and it makes you feel awful long before the blood count moves.
Iron does more than make red cells. It runs the enzymes that make energy inside every cell. It is needed to make thyroid hormone and to convert it to the active form. It is needed to make dopamine, which is why low iron shows up as low mood, poor focus and restless legs. It is needed by the hair follicle, which is why hair thinning is so often an iron story before it is a hormone story. None of that waits for anemia. It starts when the bank runs low.
The range, and where the line was drawn
Most labs mark ferritin as low only under about 15, and some go as low as 10 or 12. That line comes from older population surveys and from what predicts anemia, which is the last stage. It was never built around how a woman feels.
The guidance has been moving. In 2025 the American Society of Hematology put out draft recommendations that name 30 as the threshold for iron deficiency in adults, and say that in women with heavy periods or with symptoms, a ferritin at or under 50 is a reasonable basis to diagnose and treat. They advise against using 15 as the cutoff in menstruating women at all. Most people I know who work with fatigue and hair loss have used 50 as a floor for years. Between 15 and 30, a great many women feel every bit as depleted as the ones below the line, and the studies of tiredness and iron treatment bear that out.
So when a doctor says your ferritin is normal, the honest translation is that you are not yet anemic. That is a different thing from having enough iron.
Why women in their forties run low
The obvious reason is bleeding, and perimenopause makes it worse. As ovulation gets irregular, estrogen runs unopposed by progesterone and the lining builds thicker. Periods get heavier and closer together, sometimes for years, and every heavy month draws down the bank faster than food can refill it. Fibroids, which are common in the forties, do the same. Most women do not think of their periods as heavy because they have never had anything to compare them to. If you soak through a pad or tampon in an hour, pass clots the size of a coin, or bleed for more than seven days, that is heavy, and it is a workup on its own.
The less obvious reasons are in the gut. Low stomach acid, which rises with age and with acid blocking medicine, means iron is not freed from food. Celiac disease and gut inflammation stop it being absorbed. Coffee and tea with meals bind it. A diet low in red meat, which many women moved to years ago for good reasons, means the most absorbable form of iron is not on the plate. And a body under long stress, with inflammation running, actively hides iron away, so it is in the body and unavailable at the same time.
Why ferritin lies both ways
Here is the thing that makes ferritin a difficult number to read alone. It is also an inflammation marker. When the body is inflamed, ferritin rises, whatever your iron stores are doing. So a woman with an inflamed gut, a thyroid condition, or a hs-CRP that is quietly raised can have a ferritin of 60 and still be iron deficient. The same guidance that raised the threshold says that when inflammation is present, ferritin under 100 alongside a low transferrin saturation can still be deficiency.
This is why I never read ferritin on its own and why I ask for the whole iron picture next to the inflammation marker. One number told you the bank balance. The other tells you whether the bank is lying.
What I ask people to get
I do not order tests. I tell you what to ask for by name, and I ask you to get the printout.
Ferritin, and the number itself rather than the word normal. If it is under 30, that is deficiency by the newest guidance. Under 50 with symptoms or heavy periods is grounds to treat.
A full iron panel. Serum iron, total iron binding capacity and transferrin saturation. A saturation under 20 per cent points to deficiency even when ferritin looks fine.
A full blood count with the red cell size. Small pale cells are the late sign. Hemoglobin at the low end of normal in a woman with symptoms is worth noting, whatever the flag says.
hs-CRP alongside. So you know whether the ferritin can be trusted.
B12, folate and a full thyroid panel. Low iron and low thyroid travel together, each makes the other worse, and the fatigue looks the same from the outside. Issue 011 covers what a full thyroid panel is.
If ferritin is low and periods are not heavy, ask why. Celiac testing and a look at the gut are reasonable questions, because iron that is lost or not absorbed is a cause to find before it is a number to top up.
What I would do first
Get the number before you take anything. Iron is one supplement I never suggest guessing at. Too much iron is harmful, some people store it genetically, and a normal ferritin with symptoms often turns out to be a thyroid or B12 story instead. Test, then act.
If you supplement, ask about every other day. Absorption research over the past few years shows a single dose taken on alternate days is absorbed better than daily dosing, with less stomach upset. Take it away from coffee, tea, calcium and your thyroid medication, with a little vitamin C. If you take thyroid medication, iron needs to be at least four hours away from it, so tell your prescriber.
Put the most absorbable iron back on the plate if you can. Red meat, liver, sardines, mussels. If you do not eat meat, lentils, beans, tofu, pumpkin seeds and dark greens, always with vitamin C and never with tea.
Track your bleeding. Days, heaviness, clots. Bring it to the appointment. Heavy periods are the most common reason ferritin drops in the forties and the one most often left untreated.
Give it time and retest. Stores refill slowly. Ask for a recheck of ferritin in about three months, and if it has not moved, that is the answer to a question about absorption, and a reason to ask for an infusion conversation.
When to push harder with your doctor
Push harder if your ferritin is under 30 and you were told it is fine. If oral iron has not moved the number in three months, ask about intravenous iron, which is safe and common now. If your periods are heavy, ask for the bleeding to be treated and not only the iron, because you cannot fill a bucket with a hole in it. Ask about an ultrasound for fibroids and about the options for heavy bleeding, which include hormonal ones and a medication called tranexamic acid. If iron drops with no bleeding to explain it, or you are past menopause with a falling ferritin, that needs a gut workup and it should not wait.
If you are pregnant, the thresholds and the treatment are different and belong to your midwife or doctor. If you take blood thinners, heavy bleeding is a medication conversation before anything else.
I do not diagnose and I do not treat. I read this number next to your periods, your food, your gut, your thyroid and your life, and tell you what I see as one picture. If it needs clinical care I say so and I send you.
Questions I get asked
Is a ferritin of 15 normal?
It is inside most lab ranges and it is not enough iron to feel well. The 2025 draft guidance from the American Society of Hematology names 30 as the threshold for iron deficiency and advises against using 15 in menstruating women. Most women feel the difference between 15 and 50 clearly.
Can I be iron deficient with normal hemoglobin?
Yes, and it is the most common pattern I see. Ferritin is the store, hemoglobin is the iron already spent. The store empties first and the symptoms start then. Anaemia is the last stage, and waiting for it means waiting through years of fatigue.
What ferritin level is good for hair loss and energy?
Most clinicians who work with hair loss and fatigue aim for a ferritin of at least 50, and some prefer higher. That is a target to raise with your doctor, with a plan to retest in about three months.
Should I just start taking iron?
No. Get the number first. Too much iron is harmful, some people store it genetically, and the same tiredness can be thyroid or B12. If you do supplement, ask about alternate day dosing, which is absorbed better with less stomach upset.
Why is my ferritin high if I feel iron deficient?
Ferritin rises with inflammation, so it can read normal or high while iron is still short. Ask for transferrin saturation and hs-CRP alongside. A saturation under 20 per cent with a raised CRP is still deficiency by current guidance.
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This is general wellness education and not medical advice, diagnosis or treatment. Talk to a qualified professional, especially if you are pregnant, nursing, taking medication or managing a condition.