Dr. Carlo De la Sancha
Menu

Iron · Visual journey

Iron’s journey: where it gets in and where it slips away.

Your iron is low, you take it, and it drops again? Let’s follow it.

Drawing of the duodenum on its own: a pink, C-shaped tube leading out of the stomachDuodenumThis is where iron gets in

The way in

It all starts in the duodenum.

It’s the first part of the small intestine, right after the stomach, and it’s where iron gets into your body.

Diagram of two villi in the small intestine covered by a layer of enterocytes, with a magnified oval showing the cells, their nuclei and the microvilli on their surfaceEnterocytePasses iron into the blood

The intestinal wall

Enterocytes take it in.

The villi lining the duodenum are covered in cells called enterocytes. Iron enters these cells and passes into the blood through a doorway called ferroportin.

The end of a long bone cut open: inside, spongy bone filled with red bone marrowBone marrowThis is where red blood cells are made

Destination

It travels to the bone marrow.

Your blood carries it to the marrow, which uses it to make red blood cells. And almost all of it gets recycled.

Drawing of the liver on its own, reddish brown, seen from the frontLiverStores iron and makes the brake

Storage and the brake

The liver stores it and hits the brake.

It stores whatever iron is left over. It also makes hepcidin, the brake: hepcidin shuts the ferroportin doorway, so less iron gets in.

Micrograph of the lining of a human duodenum: finger-shaped villi, each covered by its layer of cells

Under the microscope

This is what the absorbing wall really looks like.

Two duodenal biopsies

When the villi flatten, less iron gets in.

In celiac disease, the body’s reaction to gluten flattens the villi, and less iron is absorbed.

Biopsy of a healthy human duodenum, stained with hematoxylin and eosin: tall, finger-shaped villi covered by an unbroken layer of cellsTall villi
Look at the tall fingers with space between them.Those are the villi, and that’s where iron gets in.
Duodenal biopsy from a person with celiac disease, stained with hematoxylin and eosin: an almost flat surface with no villi and elongated glands underneathAlmost flat surface
Here, the fingers are gone.The villi have flattened, leaving much less surface to absorb iron.

On a lifelong gluten-free diet, the villi heal. But don’t cut out gluten before you’re tested: doing so throws off the results.

The question

Why is my iron low when I’m already taking it?

Iron is a balancing act: what comes in versus what you lose.

The intestinal wall: villi covered in enterocytes, the cells that absorb ironEnterocyteIf the wall is damaged, less gets in
A torn blood vessel, with red blood cells spilling out of the openingBleedingEvery bleed takes iron with it
Inside a blood vessel, a macrophage (a large, pale cell) removes an old red blood cellMacrophageWith inflammation, it holds on to iron
The liver on its own, where excess iron builds upLiverExcess iron builds up here

It isn’t absorbed.

If your intestine is damaged (by celiac disease, Crohn’s disease, Helicobacter pylori or surgery), less iron gets in, even when you take it.

It’s lost through bleeding.

Heavy periods, an ulcer, colon cancer, or taking aspirin or ibuprofen often.

It gets trapped by inflammation.

Long-lasting inflammation raises hepcidin. You have iron in storage, but it doesn’t reach the marrow. Treatment is aimed at the underlying disease.

And too much does harm, too.

In hemochromatosis, the body absorbs too much iron, and the excess damages the liver, heart and pancreas. Your body has no good way to get rid of it, so iron isn’t something to take “just in case.”

What you can do

Look for the cause, don’t just reach for a pill.

Low iron always has a reason behind it. Finding that reason is what truly fixes it.

If your iron keeps dropping, ask your doctor to find out why.

Bring your lab results (complete blood count, ferritin) and ask: Am I losing blood? Am I absorbing iron well? Is there inflammation?

On your plate

Iron, with vitamin C on the side.

Beans, lentils, eggs, meat and leafy greens, paired with oranges or tomatoes. Black tea cuts down how much iron you absorb.

If you take supplements

Only with a doctor involved.

Take them only if your doctor recommends them. Your iron stores take about six more months to refill. Keep them out of children’s reach: they can be deadly.

Who’s more likely to run low

Some people need closer attention.

Pregnant women and babies, as well as people who have heavy periods, give blood often, or have cancer, digestive problems or heart failure.

If you have hemochromatosis

No extra iron.

No iron supplements, and no vitamin C supplements either.

Your friend, Dr. Carlo De la Sancha. Health and science for everyone.

Keep learning

How can a damaged intestine leave you low on iron?

Gluten and celiac disease: he was still exhausted while his intestine was being damagedWatch “Gluten and celiac disease: always exhausted, with a gut on fire”
Medical transparencySources, images and licenses

Where the information comes from

Images

The drawings are cropped from the cited illustrations. Their original labels, arrows and backgrounds were removed with code, and no structure was redrawn; the labels you see were added for this page. The micrograph of the duodenal wall is a version of the cited image with more depth, and the two biopsies are cropped and shown at the same brightness levels.

Educational content for the general public. It can’t diagnose anemia or replace a visit with your doctor: the cause and the treatment depend on your test results and on your health care team’s assessment.

Know someone who would find this helpful?

Share it with them.