Low ferritin usually means your body doesn’t have enough stored iron, most often from not getting, absorbing, or keeping enough iron due to blood loss.

What Causes Low Ferritin Levels?

Low ferritin is basically “low iron stores.” The main causes almost always fall into one of three buckets: not enough in, not enough absorbed, or too much lost.

1. Not Getting Enough Iron (Input Problem)

If your diet doesn’t supply enough iron, your ferritin slowly drops.

Common situations:

  • Vegans and vegetarians who don’t carefully replace heme iron from meat with iron-rich plant foods and vitamin C.
  • Very restrictive diets, eating disorders, or chronic under‑eating.
  • Children and teens during rapid growth spurts who outgrow their iron intake.
  • Pregnant people, because they need extra iron for the growing baby and increased blood volume.

Story-style example:
Imagine your body as a warehouse and ferritin as the shelves of stored iron boxes. If for months you only deliver half the usual boxes (low‑iron diet, pregnancy, growth), the shelves start looking bare long before the factory (red blood cells) fully runs out. That “bare shelf” stage is low ferritin.

2. Poor Absorption of Iron (Gut Problem)

Sometimes you eat enough iron, but your gut can’t pull it into the bloodstream properly.

Key causes:

  • Celiac disease or inflammatory bowel disease (Crohn’s, ulcerative colitis) damaging the intestinal lining.
  • Past stomach or intestinal surgery (e.g., bariatric surgery) that reduces absorption surface or stomach acid.
  • Long‑term use of acid‑suppressing medications like proton‑pump inhibitors (PPIs) or H2 blockers, which lower stomach acid needed for iron absorption.
  • Chronic digestive disorders that cause diarrhea or malabsorption.

In these cases, the food “arrives at the door,” but the “loading dock” (intestine) is partly shut, so the warehouse never fills.

3. Blood Loss (Output Problem)

Because most of your body’s iron is in red blood cells, anything that makes you lose blood steadily will drain your iron stores and drop ferritin.

Common sources of chronic blood loss:

  • Heavy or prolonged menstrual periods.
  • Uterine conditions causing abnormal bleeding (fibroids, adenomyosis, endometriosis with heavy periods).
  • Digestive tract bleeding:
    • Stomach or duodenal ulcers
    • Colon polyps or colon cancer
    • Inflammatory bowel disease
    • Bleeding hemorrhoids, sometimes visible, sometimes not.
  • Frequent blood donation or unrecognized small but ongoing bleeding.

A lot of people with chronically low ferritin discover a hidden source of bleeding in the gut or pelvis once doctors investigate.

4. Increased Iron Needs (High Demand)

Even if you don’t lose blood and absorb reasonably well, your body might be using iron so fast that ferritin can’t keep up.

Situations with higher demand:

  • Pregnancy and breastfeeding.
  • Rapid growth in children and adolescents.
  • High‑level endurance sports or very intense training, which can increase red blood cell turnover and small, repeated gut bleeding.

Think of this as the factory running three shifts instead of one – the warehouse empties faster unless you massively increase deliveries.

5. Chronic Diseases and Hormone/Organ Issues

Certain medical conditions can indirectly lead to low ferritin by affecting red blood cell production, hormone balance, or nutrition.

Examples:

  • Kidney disease: reduced erythropoietin (a hormone that tells your bone marrow to make red blood cells) can go along with iron problems and low ferritin, often requiring supplements.
  • Thyroid disease: hypothyroidism can be associated with heavy periods and poor metabolism, which may contribute to low ferritin in some people.
  • Chronic inflammatory conditions that reduce appetite, alter gut function, or cause low‑grade blood loss.
  • Cancer or chemotherapy, where treatment can damage rapidly dividing cells, shorten red blood cell lifespan, and disrupt nutrition.

These conditions don’t always cause low ferritin by themselves, but they often sit in the background making other causes worse.

6. Medications and Medical Treatments

Some drugs and treatments can reduce iron stores or interfere with how your body handles iron.

Key culprits:

  • Acid‑lowering drugs (PPIs and H2 blockers), taken long‑term.
  • Frequent use of certain pain medicines like aspirin or NSAIDs, which can irritate the stomach or intestines and cause slow bleeding.
  • Chemotherapy, which may increase red blood cell destruction and alter nutrition status.

If ferritin is low and you’re on these medications, doctors may consider whether they’re part of the puzzle.

7. Who Is at Higher Risk of Low Ferritin?

Certain groups are more likely to develop low ferritin and iron deficiency.

Higher‑risk groups:

  • Women of child‑bearing age, especially with heavy or frequent periods.
  • Pregnant and breastfeeding people.
  • Vegetarians and vegans who don’t plan iron intake carefully.
  • People with digestive diseases or past gut surgery.
  • Children and teens in growth spurts.

8. Symptoms That Often Go With Low Ferritin

Ferritin can be low for a while before full‑blown anemia appears, but your body often sends signals.

Common symptoms:

  • Persistent fatigue, weakness, “can’t get off the couch” feeling.
  • Shortness of breath on exertion, racing or irregular heartbeat, headaches.
  • Pale skin, feeling unusually cold, especially in hands and feet.
  • Hair loss or thinning, brittle nails, slow nail growth.
  • Restless legs, difficulty concentrating, brain fog.
  • Craving or chewing ice (pagophagia), which is oddly but strongly linked to iron deficiency.

These symptoms are not specific to low ferritin, so blood tests are essential.

9. How Doctors Figure Out Your Cause

A ferritin test is just the starting point; the real question is “why is it low?”

Typical work‑up may include:

  1. Detailed history
    • Period pattern, pregnancy history, GI symptoms (heartburn, abdominal pain, bowel changes), diet, medications, family history.
  1. Blood tests
    • Ferritin, serum iron, transferrin saturation, total iron‑binding capacity, complete blood count.
  1. Looking for blood loss
    • Stool tests for hidden blood, colonoscopy or endoscopy in some adults, pelvic evaluation in individuals with heavy periods.
  1. Screening for absorption problems
    • Tests for celiac disease, inflammatory bowel disease, or other gut conditions when suspected.

The pattern of lab results plus your story usually points to the main cause.

10. Why Low Ferritin Matters (Even Without Anemia)

Low ferritin is an early warning sign that your iron “savings account” is being drained and anemia may be next.

  • It can cause fatigue, poor exercise tolerance, and cognitive issues before hemoglobin drops.
  • Long‑term low ferritin in children can affect development and learning.
  • In adults, unrecognized low ferritin may be the first hint of serious issues like heavy uterine bleeding or hidden GI bleeding.

Catching and treating low ferritin early often prevents more serious problems.

11. Important Safety Note

  • Low ferritin has many possible causes, including some that are serious (like GI bleeding or cancer), so it should always be evaluated by a health professional.
  • Never start high‑dose iron supplements without medical supervision; too much iron can be harmful and may mask important diagnoses.
  • If you have symptoms like black or bloody stools, very heavy periods, chest pain, severe shortness of breath, or rapid worsening fatigue, seek urgent medical care.

Information gathered from public forums or data available on the internet and portrayed here.