Low ferritin, normal haemoglobin

Your iron store runs down long before you become anaemic. That is why your ferritin can be low while your haemoglobin still sits comfortably within the normal range. This is called iron deficiency without anaemia. It is no reason to panic, but it is a signal worth taking seriously: your body is drawing on its reserve. In this post you'll read what the combination means, where it comes from and what you can do about it with your GP.

Two values, two stories

Ferritin is the protein that stores iron. The amount of ferritin in your blood shows how much iron your body has in reserve: your iron store.
Haemoglobin is the protein in your red blood cells that carries oxygen. Your body needs iron to make it.

As long as there is iron in the store, your body keeps making haemoglobin as usual. Only when the store is truly empty does your haemoglobin fall, and that is when we speak of anaemia. A low ferritin with a normal haemoglobin therefore means the reserve is (nearly) used up, but your red blood cells don't feel it yet. It is the stage before anaemia. You can read more about anaemia itself in our post on anaemia.

When is ferritin "low"?

Without inflammation, a ferritin below 30 μg/L points to iron deficiency. That cut-off is higher than the lower limit some laboratories have historically used. So your result may carry no flag while your store is already low. Your GP looks at the whole picture.

Where does a low iron store come from?

A low store builds up when you lose or use more iron than you absorb. The most common causes:

Periods: Heavy periods are the most common cause in women. Some iron is lost every month, and with heavy or long periods that is more than your diet replaces.
Diet: If you eat little meat or fish, you take in less of the iron your body absorbs most easily. Vegetarians and vegans are at higher risk, especially if they don't deliberately choose iron-rich plant foods.
Giving blood: Every donation also takes iron with it. Regular donors can see their store shrink gradually.
Poorer absorption: Coeliac disease, stomach surgery or long-term use of acid-reducing medicines can reduce how much iron your gut absorbs.
Higher needs: Pregnancy, growth spurts and a lot of intensive exercise all raise your iron needs.
Hidden blood loss: Slow bleeding from the stomach or bowel often goes unnoticed. In men, and in women after the menopause who no longer have monthly blood loss, this is the cause your doctor will want to rule out.

Which complaints might you notice?

Many people with a low iron store notice little. Others do feel it:

Tiredness: The best-supported complaint. In a randomised trial, iron reduced fatigue more than a placebo in women with iron deficiency without anaemia.
Less stamina: Exercise or climbing the stairs feels harder than usual.
Difficulty concentrating: Your mind tires more quickly.
Restless legs: An uneasy, creeping feeling in the legs, mostly in the evening, has been linked to low iron.

You'll read a lot online about hair loss, dark circles or bruising. The evidence that these come from a low iron store is weak or missing. Pale skin and cracks at the corners of the mouth are mostly late signs, once anaemia is already present. In other words, you can't read iron deficiency from your face: that takes a blood test.

Why inflammation can raise your ferritin

Ferritin is more than a stock gauge. It also rises with inflammation, an infection, excess weight or liver problems. A normal ferritin then doesn't rule out a deficiency: the inflammation can mask an empty store.

That is why your doctor often also measures an inflammation marker such as CRP, or the transferrin saturation: how much iron your blood is carrying at that moment. It doesn't work the other way round: a low ferritin almost always means a genuinely empty store. Inflammation does not lower ferritin.

What to discuss with your GP

A low ferritin isn't a diagnosis in itself. It's a question: why is the store empty? A few points to take along to your GP:

Your complaints: Tiredness, less stamina, restless legs.
Your periods: Are they heavy or long? There are good treatments for that.
Your diet: Do you eat little meat or fish, or follow a vegetarian or vegan diet?
Giving blood: How often do you donate?
Stomach and bowel: Do you have stomach or bowel complaints, take acid-reducing medicines, or does coeliac disease run in your family?
Iron tablets: Whether you need them, for how long and how often. Avoid starting a long course on your own. Too much iron isn't harmless, and iron tablets can cause stomach upset, constipation or black stools.

Once your store is being topped up, a new test after a few months is a good way to see whether it's working.

Food: refilling your store step by step

Food alone refills an empty store slowly, but it does help keep it topped up afterwards:

Meat, fish and shellfish: Rich in haem iron, which your body absorbs easily. Mussels are a good Belgian classic.
Pulses: Lentils, chickpeas and beans contain plenty of plant iron.
Dark green vegetables: Spinach, kale and broccoli add extra iron.
Wholegrains and fortified breakfast cereals: A handy addition, especially on a plant-based diet.
Add vitamin C: Have an orange, a kiwi or some pepper with your meal. Vitamin C helps your body absorb plant iron.
Keep tea and coffee apart: Tea, coffee and milk slow iron absorption. Drink them an hour before or after your meal rather than with it.

In Synapse, ferritin appears in your report as your iron stores, with an explanation of what your value means and which habits fit it.

Conclusion

A low ferritin with a normal haemoglobin means your iron store is running empty before anaemia sets in. That is a good moment to catch it: the cause can often be found and the store can be refilled. Discuss with your GP where the shortfall comes from and whether you need iron. Iron-rich food and smart combinations then help keep your store at a healthy level.