Ferritin
The body's iron storage protein and the best single indicator of total iron stores. It's also an acute-phase reactant, so it rises with inflammation independent of iron status.
Low ferritin causes fatigue, hair loss, poor recovery and reduced training capacity long before hemoglobin drops into frank anemia — one of the most common correctable causes of feeling terrible with 'normal' labs.
The plan of attack
In this order. Most people start at step four, which is why they change five things at once and learn nothing.
- Confirm the number is real
An iron supplement taken before the draw. Oral iron raises serum iron and transferrin saturation for hours afterwards, which makes a deficiency panel read better than the person is. Ferritin itself moves more slowly, so the panel becomes internally inconsistent. Hold iron for 24 hours before the draw, and take the sample fasted in the morning. - Read it with its partner
Pair with the Iron Panel and hs-CRP for a complete and correctly interpreted picture. Draw it alongside: Complete Blood Count (CBC) with Differential, Iron Panel (Iron, TIBC, Transferrin Saturation), hs-CRP (High-Sensitivity C-Reactive Protein). - Work out which direction is yours
If it's high — Always interpret next to hs-CRP — inflammation raises ferritin independent of iron. Persistently high ferritin with high transferrin saturation warrants hemochromatosis genetic testing.
If it's low — Fatigue, hair shedding, cold intolerance, restless legs, poor endurance, low mood. - Fix it in this order
Nutrition. Red meat and liver are the most bioavailable sources (heme iron). Pair plant iron with vitamin C. Separate iron from coffee, tea, calcium and zinc by 2 hours — these substantially inhibit absorption.
Lifestyle. Investigate the cause of loss — heavy periods, GI bleeding, or over-donation. In men, unexplained iron deficiency warrants GI evaluation.
Supplements. Iron bisglycinate every other day — alternate-day dosing produces better absorption than daily, because daily dosing raises hepcidin and blocks uptake. Take with vitamin C on an empty stomach if tolerated. Retest before continuing long-term.
Hormones. Treat heavy menstrual bleeding (a gynecological conversation). If donating blood for hematocrit control, space donations and monitor ferritin.
Compounds. The classic TRT trap: donate blood repeatedly to control hematocrit → tank ferritin → feel exhausted → blame testosterone. Track both together, always.
Work down the list, not across it. Adding a compound on top of an unfixed diet is why generic protocols fail. - Retest
8–12 weeks after starting iron; every 6 months if donating blood. Change one thing at a time, or the retest can't tell you which thing worked.
How to fix it
📚 WHO ferritin threshold guideline. Camaschella C, NEJM 2015 — iron-deficiency anemia. Stoffel NU et al., Lancet Haematol 2017 — alternate-day iron dosing.
🩸 Test your Ferritin
Order directly through Marek Diagnostics — no doctor's visit needed, drawn at any Quest location in the US. Code CAMERON applies 10% off automatically.
Order this test — 10% off → Browse all 102 markers →What Ferritin is usually tested alongside
On its own, one marker is a data point. These panels include Ferritin plus the markers that make it interpretable — each names every test, why it is on the list, and loads the whole set into your cart in one click at 10% off.
includes this + 11 more markers — Persistently exhausted despite adequate sleep, and either haven't been tested or were told everything is normal.
includes this + 6 more markers · built for men — Never had proper bloodwork, or want the highest-value snapshot for the least money.
includes this + 6 more markers · built for women — Exhausted, breathless on stairs, hair shedding, brittle nails, restless legs, brain fog — and you've been told your blood count is normal. Extremely common in menstruating women, endurance athletes, and anyone plant-based.
includes this + 9 more markers · built for women — Widening part, thinning at the crown, more hair in the shower drain, or a ponytail that's visibly thinner than it was.
What moves your Ferritin
3 compounds and 11 supplements in the Vault have a documented effect on this marker, or are a reason to have measured it first:
Browse all 237 compounds & 350 supplements →
Would you feel it? Symptoms Ferritin helps explain
People rarely search for a marker — they search for how they feel. These are the complaints where this marker is worth checking, and whether it is a first-line test or a follow-up once the obvious causes are ruled out.
Why your Ferritin might be wrong
Most abnormal results are interference, not disease. These are the things that measurably move this specific marker — check them before you change anything. Each one says whether the number is wrong and should be repeated, badly timed and should be redrawn, or real with a cause worth explaining.
Oral iron raises serum iron and transferrin saturation for hours afterwards, which makes a deficiency panel read better than the person is. Ferritin itself moves more slowly, so the panel becomes internally inconsistent.
Hold iron for 24 hours before the draw, and take the sample fasted in the morning.
Ferritin is an acute-phase reactant. Inflammation drives it UP independently of iron stores, so a normal-looking ferritin can sit on top of genuine iron deficiency. A recent illness, an injury, or a heavy training block all do it.
Read ferritin next to hs-CRP. If CRP is up, the ferritin is not trustworthy as an iron measure — repeat both once the inflammation settles.
Ferritin is an acute-phase reactant as well as an iron store. Infection, injury, obesity, hard training and liver stress all raise it — so a 'normal' ferritin of 60 alongside a CRP of 8 may be a depleted ferritin of 20 wearing a disguise. This is the single most consequential interference in the whole Vault, because it causes real iron deficiency to be missed.
Never read ferritin without a CRP beside it. If CRP is up, lean on transferrin saturation instead.
Rises acutely for days after hard exercise, which produces a falsely reassuring number in exactly the athletes most likely to be deficient.
Draw at least 48–72 hours after a hard session.
Recent dosing raises measured ferritin above your true stored level — supplemental iron shows up in the tank before it has actually filled it.
Stop iron 5–7 days before a draw meant to assess your baseline.
Lowers ferritin substantially; can falsely lower HbA1c by shortening red cell lifespan.
Track ferritin every time you donate — the classic TRT trap. Note recent donation when reading HbA1c.
Raises inflammatory markers and ferritin; suppresses testosterone and T3 (nonthyroidal illness).
Wait 2–4 weeks after an illness before drawing — otherwise you're measuring the infection, not your baseline.
What Ferritin means in combination
A single marker tells you a little. Combinations tell you the story — these are the named patterns this marker takes part in, and what each one points at.
Low energy availability shuts the reproductive axis down to save fuel. It is not a badge of being lean — it costs bone density in a way that does not fully come back.
Eat more. That is the treatment, and no supplement substitutes for it. Get bone density assessed if it has been going on for a year or more. The RED-S panel exists for exactly this picture.
Female pattern shedding is very often nutritional and thyroidal before it is hormonal. Each of these alone can shed hair; together they reliably do.
Ferritin above 50 is the usual threshold for regrowth — normal is not the same as sufficient here. Fix all three and give it 3–6 months; the hair cycle is slow and nothing shows in weeks.
Converting T4 into active T3 needs selenium, iron, zinc and adequate energy. When those are short — or under stress and illness — you make inactive reverse T3 instead.
Adding more T4 to a conversion problem does not work. Correct ferritin and selenium first, address energy availability and stress, and retest in 8–12 weeks before changing any thyroid medication.
The classic TRT trap. Repeated phlebotomy to control hematocrit depletes iron stores. You fixed the viscosity and created iron-deficiency fatigue.
Track ferritin every time you donate. Supplement iron (bisglycinate, alternate-day dosing absorbs better) and re-evaluate whether the TRT dose/frequency itself is driving the hematocrit up.
What to test next
Markers rarely answer alone. These are the ones that put Ferritin in context — each with its own full breakdown.
Frequently asked questions
30–400 ng/mL Ranges vary by laboratory and assay — always compare to the range printed on your own report.
>50 ng/mL minimum; ~75–150 ng/mL for energy and hair.
Always interpret next to hs-CRP — inflammation raises ferritin independent of iron. Persistently high ferritin with high transferrin saturation warrants hemochromatosis genetic testing.
Fatigue, hair shedding, cold intolerance, restless legs, poor endurance, low mood.
You can order Ferritin directly through Marek Diagnostics without a doctor's visit — drawn at any Quest Diagnostics location in the US. Code CAMERON applies 10% off automatically.