Low Ferritin: The Iron Story Your Bloodwork Might Miss

You eat well, you sleep enough, yet you're still tired. The answer might not be in your diet, but in your iron reserves, and standard bloodwork doesn't always catch it.

Part one

Two kinds of iron deficiency

Most people think of iron deficiency as anaemia: low red blood cells, confirmed by a simple blood test. But there's a second, quieter version that rarely shows up that way. It's called functional iron deficiency, and it can leave you exhausted while your bloodwork still reads "normal".

The difference sits in two numbers your doctor can measure. Haemoglobin tells you how much iron is circulating right now. Ferritin tells you how much iron you have in reserve, your body's savings account. Ferritin drops long before haemoglobin does, which means you can feel the deficit for months before a standard test flags anything.

13–30 µg/L

the range most standard blood tests use to flag deficiency, calibrated to prevent anaemia, not to define feeling well

75–120 µg/L

the range functional practitioners consider genuinely optimal for steady energy, focus and mood

In other words: your ferritin can sit just inside the "normal" box on paper, and you can still feel flat, foggy and wiped out. Some practitioners report that most people notice a real difference in symptoms once ferritin climbs well above the threshold labs use to say you're fine, closer to that 75 µg/L mark.

Part two

The signals your body sends

Low iron doesn't always announce itself clearly. It tends to show up as a collection of smaller signals that are easy to blame on stress, poor sleep, or "just getting older".

Physical

Persistent fatigue
Hair loss
Brittle nails
Shortness of breath
Pale skin
A racing or fluttering heart
Dizziness
Cold hands and feet
Restless legs

Mind & mood

Brain fog
Trouble concentrating
Mood swings
Irritability
Lower libido
Memory lapses
Unexplained anxiety

"Fatigue isn't a personality trait. Sometimes it's simply your iron reserves asking to be refilled."

Part three

Six common reasons ferritin runs low

Heavy or prolonged periods. Regular blood loss depletes reserves faster than most diets can refill them.
Poor absorption. Low stomach acid, coeliac disease, IBD or long-term use of acid-reducing medication all reduce how much iron you actually take up.
Higher demand. Pregnancy, breastfeeding, growth spurts and endurance training all raise your iron needs.
A plant-based diet. Iron from plants absorbs far less efficiently than iron from animal sources, so it needs more attention, not more restriction.
The postpartum period. Birth itself, plus recovery, can leave reserves running low for months afterwards.
Chronic inflammation. This is the sneaky one. Inflammation can block iron uptake even when you're eating enough of it, which is part of why gut health and iron levels are so closely linked.

Did you know

One molecule of ferritin can store up to roughly 4,500 iron atoms. Think of it as a microscopic vault inside your cells, quietly holding iron in reserve until your body calls for it.

Practical

Pair iron-rich meals with vitamin C: a squeeze of lemon over lentils or spinach noticeably boosts absorption.
Coffee and tea contain compounds that block iron absorption. Enjoy them between meals rather than with them.
Cooking in a cast-iron pan, especially with acidic ingredients like tomato sauce, can add small amounts of iron to your food.

Part four

What actually helps

Iron deficiency responds well to attention, but rarely to guesswork. A few starting points:

Ask for ferritin specifically. A standard check often measures haemoglobin alone. Request ferritin too, to see your actual reserves, not just what's circulating.
Feed your reserves, not just your plate. Red meat, organ meats, shellfish and dark poultry offer the most easily absorbed iron. Lentils, spinach, tofu and pumpkin seeds are strong plant-based sources, especially paired with vitamin C.
Look upstream. If levels stay low despite eating well, the cause is often absorption or inflammation, not intake. That's where a fuller picture of your gut and symptoms becomes useful.
Consider medical support for bigger gaps. For more significant deficiencies, options like iron infusions exist under medical guidance, particularly when oral iron isn't tolerated or absorption is impaired.

To remember

Two numbers matter: haemoglobin (iron circulating now) and ferritin (your reserves).
"Normal" on a lab report and "feeling well" aren't always the same range.
Fatigue, brain fog and mood dips can all trace back to low ferritin.
Vitamin C helps you absorb iron; coffee and tea taken with meals work against it.
If symptoms persist, ask specifically for a ferritin test, not just haemoglobin.

This article is for educational purposes and does not replace medical advice. If you recognise these symptoms, speak to your doctor and ask about a ferritin test.