Ferritin for runners: why "normal" might not be enough
Ferritin is the protein that stores iron, and the blood test for it is the best everyday measure of how much iron you have in reserve. For runners it is one of the most useful numbers on a report, because iron runs short long before the classic signs of anaemia appear.
Why runners run low
Endurance training leans on iron harder than most sports. You lose a little through sweat, a little through the gut, and in runners a little more through foot-strike haemolysis, where red cells are damaged with every footfall over long distances. Add a period, a plant-based diet or a heavy training block, and stores can slide for months while haemoglobin still looks fine.
The result is a familiar story: flat legs late in a session, a heart rate that will not settle, recovery that drags, and a report in which everything is "normal".
The number sports medicine uses
Laboratory reference ranges for ferritin start low, sometimes in single figures, because they describe the general population. Sports medicine takes a different view. A widely cited Swiss consensus on iron deficiency in sport treats ferritin below 15 µg/L as depleted stores and 15 to 30 µg/L as low stores, and uses 30 µg/L as the practical cut-off for adult athletes. Several studies of endurance athletes use the same 30 µg/L line, and the consensus suggests aiming higher, around 50 µg/L, before altitude training.
So a ferritin of 22 can sit comfortably inside a laboratory's range and still be low for someone running 60 miles a week. That is why every Skyline report shows the laboratory range and, for markers like this, the context that matters for people who train.
Read it with the rest of the iron panel
Ferritin also rises with inflammation and infection, so a normal or high result during a cold, after a race or with a niggling injury can hide a real shortage. The Health Profile and above pair it with serum iron, transferrin, total iron-binding capacity and transferrin saturation. Low saturation with high transferrin confirms that iron supply is short; high ferritin with high saturation is a different conversation entirely and worth raising with your GP, because it can point to iron overload.
What to do with a low result
- Take the report to your GP. The decision to supplement, and at what dose, is theirs, and iron taken without a reason can do harm.
- Look at intake and timing: red meat, pulses, fortified cereals, and vitamin C with plant sources; tea and coffee away from iron-rich meals.
- Retest after 8 to 12 weeks. Ferritin moves slowly, and the trend tells you more than one reading.
This article is educational. It explains what a marker is and what can move it; it does not interpret your results or replace advice from your GP.
