Understanding your ferritin and haemoglobin results

If you've been feeling flat and your GP has run bloods, chances are you've been handed two numbers: ferritin and haemoglobin. They're related, but they measure different things - and understanding the difference explains why iron deficiency can drag on for months before anyone calls it anaemia.

Ferritin: your iron savings account

Ferritin is a protein that stores iron, and the blood test is used as a proxy for how much iron your body has in reserve. Think of it as your savings account. A low ferritin means your reserves are running down - even if you're still functioning day to day. In New Zealand, laboratory reference ranges vary slightly, but a ferritin below about 20-30 micrograms per litre generally indicates depleted iron stores, and symptoms can appear well before the number bottoms out.

One wrinkle worth knowing: ferritin also rises with inflammation, infection and some chronic conditions. That means a 'normal' ferritin doesn't always rule out iron deficiency - which is why results should be interpreted by a clinician who knows your history, not read off a chart in isolation.

Haemoglobin: your delivery trucks

Haemoglobin (Hb) is the iron-containing protein in red blood cells that carries oxygen around your body. If ferritin is the savings account, haemoglobin is the fleet of delivery trucks currently on the road. When iron stores run out, your body can no longer build enough healthy red blood cells, haemoglobin falls, and you have iron deficiency anaemia - the stage where tiredness, breathlessness and pale skin tend to become hard to ignore.

Why you can feel awful with 'normal' haemoglobin

This is the part many people find validating: you can be significantly iron deficient - exhausted, foggy, losing hair - while your haemoglobin is still within the normal range. Iron deficiency without anaemia is real, common (especially in menstruating women), and worth treating. Waiting until anaemia develops is like waiting until the trucks stop running before refilling the warehouse.

What happens with these numbers at VitalLine

• When you book an iron assessment, you upload your recent blood results directly in the booking form.
• Ferritin and haemoglobin, alongside your screening answers, are reviewed by the prescriber to confirm an infusion is appropriate and whether you meet funding criteria.
• Bloods usually need to be recent - within the last few weeks - because iron levels change over time.
• If your results don't support an infusion, we'll tell you honestly. Oral iron is the right answer for many people, and that's a good outcome too.