All the girlies are low in ferritin and writing about it. So, let’s dig in.
It is close to literal…I’m telling you.
The CDC’s 2026 Nutrition Report puts low ferritin at about 18% of US women of reproductive age in 2021 to 2023, up from about 13% in 2003 to 2004.
Most of them keep adding iron and stay low.
That’s the pattern I see most.
Someone gets a result back that says 12, or 17, or 24. They are handed a bottle of iron, or they buy one. Three months later, the number has barely moved, and now they also have constipation and a stomach that hurts.
Iron going in is only half of the equation.
The other half is how much your gut absorbs, how much you lose, and how much your body locks away.
If ferritin stays low, one of those three is the problem, and a bigger dose of the same thing will not fix it.
Last week, I shared my own labs. My ferritin was 17, which is low. My iron, iron saturation, and hemoglobin all came back very healthy and in range, however, so a standard panel would say I’m fine.
Ferritin, your iron storage marker, is the first number to drop, long before anything shows up as anemia, which is why I test it. So, this one is personal, and here are the ten reasons I look for first.
A quick note on the number, as labs flag it low at different cutoffs.
The World Health Organization uses 15 ng/mL, and hematology guidance now suggests 30. Some treatment guidelines aim for 50 or higher once you’re rebuilding stores.
Ferritin also rises with inflammation, so a number inside the “normal” range does not rule out low iron.
Ten main contributors worth looking into
Low stomach acid or long-term acid blockers
Iron from food and supplements needs an acidic stomach to absorb well. If you have been on a proton pump inhibitor or an antacid for years, or your acid is low for other reasons, you can eat plenty of iron and absorb very little of it. This is the first thing I check, and I wrote about it in my low stomach acid piece. Don’t stop a prescribed medication without talking to your prescriber.Gut inflammation and H. pylori
H. pylori is a stomach bacterium linked to low iron, and it also suppresses stomach acid. Ongoing gut inflammation from any source makes the lining a poor absorber. Testing for H. pylori is simple and worth doing if your ferritin is low and no one can explain why.Celiac disease and other malabsorption
Unexplained low iron is a recognized early sign of celiac disease, which is why guidelines call for a celiac screen. Crohn’s and colitis do the same thing. If you have low ferritin plus bloating, loose stools, or a family history, ask for celiac screening before you change anything about your diet, because going gluten-free first can make the test unreadable.Heavy periods
This is the most common cause in women who still menstruate. Soaking through a pad or tampon every hour or two for several hours in a row, passing large clots, or periods longer than a week all count. Heavy periods are also worth investigating for their own sake, since fibroids, adenomyosis, endemetriosis, and other forms of hormone imbalance can sit behind them.Slow blood loss in the gut
This one needs a doctor, not a supplement. Ulcers, polyps, hemorrhoids, and regular use of ibuprofen or aspirin can cause small losses of blood that you never see. If you are a man, or a woman past menopause, with low ferritin, you need to find out where the iron is going. That’s a conversation about a GI workup, and it should not wait.Chronic inflammation
When your body is inflamed, it makes more of a hormone called hepcidin. Hepcidin tells your gut to absorb less iron and tells your cells to hold on to the iron they already have. The result is low available iron even if your intake is fine. It also means ferritin can look normal or even high during inflammation while your body is functionally short on iron. This is why one number is never enough.Your diet and what you drink with it
Iron from red meat and organ meats absorbs much better than iron from plants, and NIH sets the target for vegetarians at nearly twice the usual amount for that reason. If you eat little red meat, you are working with a smaller margin. Coffee, black tea, matcha, green tea, and calcium taken with a meal reduce absorption of plant iron, so give them about an hour of space from meals and from any iron supplement. You don’t have to give up matcha.Frequent blood donation
Each donation takes a meaningful amount of iron with it. Regular donors often run low on stores, even when hemoglobin is fine.Demand that outruns supply
Pregnancy, the postpartum months, breastfeeding, and heavy endurance training all raise how much iron your body needs. Intense exercise also appears to raise hepcidin for a few hours afterward, which makes absorption harder in the very window when you want it. If you’re trying to conceive, add ferritin to your checklist. A small 2023 study of 72 women found ferritin under 30 in 33% of women with unexplained infertility and 11% of women without it. That shows an association, not proof of cause, but it is a simple blood test.Parasites and gut infections
Some parasites, hookworm being the clearest example, cause blood loss in the gut. Others damage the lining and impair absorption. This matters most if you’ve traveled, have had a bout of food poisoning that never fully resolved, or have digestive symptoms that started after a trip. A stool test is how you find out. I would not guess.
What to ask for before you blindly take more iron
Ask for the full iron panel, not ferritin alone: ferritin, serum iron, TIBC (total iron binding capacity), transferrin saturation, a CBC, and a marker of inflammation such as hs-CRP.
Together, these show whether your stores are low, whether iron is getting delivered, and whether inflammation is distorting the picture. Too much iron is also harmful, and some people carry too much, so this is not something to guess at with a bottle.
A transferrin saturation under about 20% is another sign iron is running low. If you take an iron supplement, ask your lab whether to pause it for a day or two before the draw, since a recent dose can inflate your serum iron.
What to do about it
Start with the root cause before anything else. If a gut infection, low stomach acid, or heavy periods are behind the number, iron alone will not hold it. That includes supplements. Iron without the underlying issue addressed is likely not going to move the needle much, or very fast, so expect a slow climb until the cause is handled.
Food comes first. Red meat, liver, oysters, and sardines carry heme iron, which absorbs better than the iron in plants (roughly 15 to 35% versus 2 to 20%). Plant sources include pumpkin seeds, lentils, beans, chickpeas, tahini, and cooked leafy greens such as kale and collards. Spinach counts too, but it absorbs less because of oxalates. Soak or sprout lentils and seeds when you can, pair plant iron with a vitamin C food like bell pepper, citrus, or tomatoes, and keep coffee, black tea, matcha, green tea, and calcium at least an hour away from iron-rich meals and from any iron supplement. Cooking in cast iron adds a little more.
Consider supplements, but only if you can absorb them. If your doctor recommends a supplement, ferrous sulfate is the standard form. Iron bisglycinate has been linked to fewer stomach side effects in trials, mostly in pregnant women and children. Some research suggests that taking iron every other day absorbs better per dose than daily, with similar gains in hemoglobin, and it may be easier on the stomach. Take it at least four hours apart from thyroid medication, check the label for elemental iron per serving, and recheck ferritin after about 6 to 12 weeks.
Consider an iron infusion. Iron infusions are reserved for people who can’t tolerate or absorb oral iron, are losing blood faster than they can replace it, or have not responded to a proper trial of oral iron. That’s a decision for your doctor and/or hematologist.
What I do with this
In my work, low ferritin is rarely a supplement problem. I look at stomach acid, gut lining, drainage, inflammation, and losses, in that order, and I treat what is in the way before I add anything.
If you want to see how I sequence all of that, join me for The Blueprint, my free live masterclass on Tuesday, November 17 at 12 PM PT / 3 PM ET. I walk through the full five-phase method and take live questions.
Meghan is a Functional Health + Detox Practitioner, not a medical provider. This post is for education only and is not medical advice. Low ferritin has several possible causes, some of which need medical evaluation, so please work with your doctor alongside any holistic approach.
Which of these ten sounds most like you? Tell me in the comments, or reply if you’re reading this in your inbox. I read every one. I can’t interpret individual labs, but I can point you to what to ask for.
If you want to start where your body actually needs you to start, with your exits, download my free Drainage Starter Guide. You’ll also get my private newsletter, which is where masterclass invitations, cohort openings, and waitlists go first.
Ready to dive deeper? Join me for The Blueprint, my free live masterclass on November 17 at 12 PM PT. I’ll walk through the full detox sequence and take your questions live.
Want to do this work 1:1? I have a few spots open this fall. Book a free intake call.
And, if you have any other questions or comments, don’t hesitate to ask me any time in my weekly Q&A in my chat.
If you found this helpful, here’s how you can help:
Tap the heart so that I know it resonated
Leave a thoughtful comment—I read and appreciate every one!
Forward to a friend who might need to hear it
Share it with your community on Substack Notes, Instagram (tag @meghanswidler), or LinkedIn (and tag me there too!)
Upgrade to a paid subscription below to support deeper work like this
Your support means more than you know.
Not on my private newsletter yet?
That’s where masterclass invitations, cohort openings, and waitlists go. Substack essays cover the writing. My newsletter covers the offers.
Thanks Meghan, this is great info! makes sense, too.