Your blood test came back normal. You are still exhausted.

Both are true, and one number nobody showed you explains why.

Iron deficiency does not arrive all at once. It is a slope. Your body quietly draws down its iron stores long before your haemoglobin drops far enough to be called anaemia. That earlier stage has a name, iron deficiency without anaemia, and it is at least twice as common as the anaemia everyone screens for. The marker that catches it early is ferritin, which reflects your iron stores. Haemoglobin, the number most people are given, only falls once those stores are already running empty. By then you have been tired for a long time.

The scale of it is easy to underestimate. Iron deficiency anaemia affects more than a billion people worldwide, and the non-anaemic version is more common still. It lands hardest on menstruating women, with prevalence around one in five by the strict thresholds and considerably higher by the thresholds many researchers now argue we should be using. That cut-off is the catch. The standard ferritin threshold has been criticised for years for being set too low, which means women are routinely told they are fine while sitting just above a line that does not reflect how they actually feel.

Why does this matter when you are not technically anaemic?

Iron does far more than carry oxygen. Low stores are linked to fatigue, poor concentration, reduced exercise capacity and low mood, with or without anaemia in the picture. Controlled trials in non-anaemic women with unexplained fatigue and low ferritin have shown that correcting the iron improves how they feel and what they can do. The tiredness was not imagined. It had a cause the usual test was never designed to find.

The phrase "your bloods are normal" has ended more investigations than it ever should have.

Normal is a range built around a population. It is not a verdict on you.

If you are flat, foggy and tired in a way rest does not touch, ferritin is one of the first numbers I would want to see, and I would want to know exactly where it sits, not merely whether it cleared the lowest possible bar.

Imagine knowing precisely what your body is short of, instead of being told for the third time that nothing is wrong.

The answer is in the numbers nobody ran. Get to know your body → https://www.sannalife.health

Sources: 

• American Society of Hematology systematic review and meta-analysis on iron deficiency prevalence (Blood, 2025); 
• Lancet Global Health on physiologically based ferritin thresholds (2025); 
• PMC review, iron deficiency without anaemia; Lausanne randomised controlled trial on iron and fatigue in non-anaemic women.