Iron Deficiency Without Anemia: The Hidden Diagnosis

It’s a busy Monday morning, and you walk in to see a 4-year-old child for her well check. Her parents mention she’s been more tired and moody lately, but otherwise, she’s a happy, healthy kid—just a bit of a picky eater. So, you check her Hemoglobin level… and it comes back perfectly normal. 

Great! You reassure the parents, talk about healthy sleep habits, maybe even offer some helpful behavioral tips. Ready to move on to the next patient, right?

Not so fast. You’ve ruled out anemia. But have you ruled out iron deficiency (ID)? 

In our January 2025 episode of Peds RAP, I sat down with Pediatric Hematologist Dr Chris Denton to talk about a diagnosis that all too often remains hidden: iron deficiency without anemia. 

Why Does Iron Deficiency Without Anemia Matter?

Many of us were taught that iron deficiency only really matters because it can lead to anemia. So, if the hemoglobin is normal, we feel pretty reassured that a kiddo’s iron stores are probably fine. 

But it turns out that approach can miss important cases. Iron deficiency without anemia is all too often undiagnosed. Even without anemia, low iron can lead to:

• Cognitive problems: Brain fog, fussiness, learning difficulties, and attention difficulties
• Exercise intolerance: Kids who struggle to keep up in PE or get winded faster than their peers
• Immune dysfunction: Research suggests iron-deficient kids may have a blunted immune response to vaccines
• Mood problems:  Hard to tease out in toddlers or moody teens, but worth keeping in mind
• Sleep disturbances: Low iron can lead to a variety of sleep disturbances

Some conditions are especially linked to low iron, including:

• Breath Holding spells
• Restless Legs Syndrome
• Neurodevelopmental conditions like Autism, ADHD and learning disorders

How Should You Diagnose Iron Deficiency?

You can’t diagnose what you don’t test for. Dr. Denton’s key takeaway? If you suspect iron deficiency, go beyond hemoglobin—check iron stores.

A full iron panel typically includes:

• Complete Blood Count (CBC)
• Iron level
• Total Iron Binding Capacity (TIBC)
• Ferritin

Alternatively, you can screen for iron deficiency by checking CBC and ferritin level. Ferritin measures iron stores, and it’s a pretty sensitive measure of early iron deficiency. But keep in mind that ferritin is an acute phase reactant, so it can be elevated if your patient is sick—which can mask underlying iron deficiency. 

Who Should Be Screened for Iron Deficiency?

Infants

The 2010 AAP guidelines recommend universal hemoglobin screening at 12 months. For high-risk infants, Dr. Denton and the AAP recommend adding an iron assessment (e.g., ferritin).

High-risk infants include those with:

• Prematurity
• Low birth weight 
• Exclusive breastfeeding beyond 4 months without supplemental iron
• Infants with poor feeding, inadequate nutrition

Note that some argue we should be screening all children with a ferritin level. Greer et al. published a commentary in Pediatrics in 2022, arguing that pediatricians should screen all infants at 12 months of age with a hemoglobin check and a measure of iron, such as serum ferritin. 

Older Children & Adolescents

Consider screening in: 

• Children presenting with clinical signs of iron deficiency: fatigue, dizziness, pallor, palpitations
• Picky eaters
• Children with GI issues/absorption problems
• Anyone with chronic blood loss (like menstruating adolescents)
• Children with neurodevelopmental conditions like Autism, ADHD, and learning differences

There aren’t official guidelines on screening neurodivergent kids for iron deficiency, but Dr. Denton recommends screening at least once for ID based on its strong correlation with these conditions.

How Do You Treat Iron Deficiency?

Oral Iron

For most cases, oral iron is the way to go. Here are Dr. Denton’s top treatment pearls:

• Formulation: Ferrous sulfate is the fastest and most effective formulation—but it tastes terrible. If it’s not tolerated,  polysaccharide iron is a more palatable alternative.

• Dosing: The recommended dosing for children is 3mg/kg/day
  • This is the dose Dr Denton recommends since the body doesn’t seem to absorb well beyond this amount. 
• Frequency: Once daily is best—twice-daily dosing actually reduces absorption due to hepcidin release.
  • Every other day dosing is probably as effective as daily dosing. But daily dosing is usually best for compliance. 

IV Iron

An exciting development in the world of Hematology is the newer option of IV iron infusion. These infusions last about 30 minutes and can lead to improvement in hemoglobin in just a few days. 

IV iron is usually considered 2nd line, to be used in cases where oral iron treatment has failed. But there are some cases in which it’s reasonable to consider IV iron as 1st line. This includes: 

• Severe anemia (typically defined as hemoglobin less than 5)
• Anticipated poor response (severe behavioral problems, h/o poor compliance, severe constipation, inflammatory GI condition that could lead to poor absorption)

The only FDA-approved IV iron for kids is ferric carboxymaltose, which can replete iron stores in one or two infusions.

• Potential side effects? Mild rash, hypophosphatemia, and very rarely, anaphylaxis. But overall, it’s well-tolerated.

I was especially excited to learn more about IV iron infusions for kids. Those of us who have had to chase down a child to convince them to take the yucky liquid that could also stain their teeth (not to mention their clothes!) can marvel at how one infusion can replace months of nightly battles. 

So next time you see a tired, moody, picky-eating toddler—or a teen who just can’t seem to keep up in PE—pause before moving on. Even if that hemoglobin is normal, there might be a hidden diagnosis underneath it all. One you can only diagnose if you know to check.

And if you want even more insights on iron deficiency, check out our full conversation with Dr. Denton, "Iron Deficiency without Anemia" on Peds RAP—because sometimes, the diagnosis is hiding right under our noses.