The Short Answer
Ferritin measures your stored iron, and it falls before haemoglobin does. Because most standard blood tests check haemoglobin rather than ferritin, your iron can be depleting for months — leaving you fatigued and foggy — while your results still look normal.
“My blood test came back fine.”
If you’ve said these words to yourself while still feeling exhausted, foggy, and watching more hair fall out than usual, this post is for you.
The issue isn’t that your doctor missed something. The issue is that most standard blood tests check haemoglobin, and haemoglobin is one of the last markers to drop when iron is depleted.
If you want to know whether your iron stores are healthy, you need to check ferritin. And those are two very different things.
Key Takeaways
- Ferritin is your iron savings account — it falls first when iron runs short.
- Haemoglobin is one of the last markers to drop, so it misses early to moderate deficiency.
- Symptoms can appear while ferritin is still technically “normal” but trending low.
- Heavy periods, plant-based diets, gut conditions, and heavy training all deplete ferritin.
- Ferritin isn’t automatic on a blood panel, so ask, “was my ferritin checked?”
What is ferritin, exactly?
Ferritin is a protein that binds to and stores iron in your body. Your ferritin level reflects your iron reserves, specifically, how much your body has banked for future use.
Think of it as the savings in your bank account, while iron is the cash you keep in your wallet. When the circulating iron dips, your body withdraws from ferritin to top it back up, the same way you’d visit an ATM when the cash in your wallet runs low.
If your iron intake is consistent and absorption is working properly, ferritin stays stable. When iron demand outpaces supply, such as through heavy periods, poor absorption, high physical activity, or not eating enough iron-rich foods, ferritin starts to fall.
Your ferritin can be declining for weeks or months before any other blood marker registers a problem. Your body will defend haemoglobin levels for as long as it can by depleting its ferritin stores to keep them stable. By the time haemoglobin drops, iron deficiency has often been progressing for a while.
Can symptoms appear before the numbers flag anything?
Symptoms of iron deficiency, particularly fatigue, hair loss, poor concentration, and low mood, can begin to appear before ferritin hits the clinical threshold that would trigger a formal diagnosis.
You can be symptomatic before you’re technically deficient by lab definition.
This is why so many women end up feeling frustrated that while their symptoms are real, their blood test looks normal, and nobody seems to have an explanation. The explanation is often ferritin that’s trending downward but hasn’t crossed the clinical threshold yet.
What does a “normal” ferritin level actually mean?
This is worth discussing with your doctor, because the clinical definition of normal ferritin and the functional range for feeling your best are not always the same thing.
Standard laboratory reference ranges for ferritin tend to be quite wide, mainly because they are set at the population level to capture the most severe cases. Functional medicine practitioners and specialists in iron deficiency often work with tighter reference ranges, particularly for women who are symptomatic.
You may receive a ferritin result that falls within “normal” range, and your doctor may reassure you that it’s fine — but if your result is on the lower end of that range and you’re experiencing symptoms, it may be worth investigating further.
At New Path, we look at ferritin results in context, and not just whether they fall within the lab’s reference range, but where they sit, what your symptoms are, and what underlying condition(s) may likely be driving any depletion.
What causes ferritin to drop?
There are several common reasons ferritin depletes, many of which are easy to overlook:
- Heavy periods — one of the most significant causes of iron depletion in women. Even periods that seem ‘normal’ can cumulatively deplete stores over time.
- Poor dietary iron — particularly in those following plant-based diets, where non-haem iron absorbs at roughly 5% versus 25% for haem iron from meat.
- Gut absorption issues — conditions like IBS, coeliac disease, or Crohn’s disease can reduce how much iron your body absorbs from food, even if your intake is adequate.
- High training load — athletes and regular gym-goers have higher iron demands, and red blood cell breakdown during high-impact exercise can accelerate depletion.
- Pregnancy or recent postpartum — iron requirements increase during and after pregnancy.
Why might you need to specifically request a ferritin test?
Ferritin is not automatically included in most routine blood panels. A standard full blood count checks haemoglobin, white blood cell count, and platelet count. Ferritin has to be specifically ordered.
If you’re experiencing symptoms and have had blood work done recently without feeling better, it’s worth asking your doctor: “Was my ferritin specifically checked?” If it wasn’t, that’s your next step.
What happens after testing?
If your ferritin comes back low, or low-normal with symptoms, treatment depends on how depleted your stores are.
For mild or borderline deficiency, oral iron supplementation combined with dietary changes is usually the first approach. For moderate to severe deficiency, or for patients who’ve tried supplements without success (due to side effects or poor absorption), an IV iron infusion is often the faster and more effective route.
An IV iron infusion delivers iron directly into the bloodstream, bypassing the digestive system entirely. Absorption is not an issue, and the digestive side effects that make oral iron supplements hard to sustain simply don’t occur.
Catching falling ferritin before haemoglobin drops is the whole point. By the time a standard blood test flags anaemia, the deficiency has usually been affecting how you feel for months. The earlier you test, the simpler the correction.
Frequently Asked Questions
What is ferritin?
Ferritin is a protein that binds to and stores iron in your body, so your ferritin level reflects your iron reserves. When intake or absorption can’t keep up with demand, ferritin falls before other iron markers.
Can ferritin be low with a normal blood test?
Yes. Most standard tests check haemoglobin, which the body defends by drawing down ferritin. Ferritin can be low for weeks or months before the haemoglobin level registers a problem.
What causes low ferritin?
Common causes include heavy periods, low dietary iron (especially plant-based diets), gut absorption issues like IBS, coeliac or Crohn’s disease, high training loads, and pregnancy or recent childbirth.
What ferritin level is considered low?
Reference ranges vary by lab and are set wide at the population level. Many women are symptomatic at low-normal ferritin, so it’s worth reviewing your specific number with your doctor rather than relying on the “normal” flag.
Ready to check your iron?
A simple ferritin test shows what a standard blood test can miss. Our iron deficiency screen checks both ferritin and haemoglobin at just $68 nett. No fasting required, and results available in 1-2 days.
