Iron Blood Test Tips

34% of menstruating females are seen as deficient in iron

Iron supplements Stop for 3 days before a blood test otherwise it will elevate Transferrin saturation levels and give a false ferritin surplus reading.

Alcohol Avoid the night before as alcohol increases iron availability and gives a false high reading

Strenuous exercise Avoid for 2 days prior to a blood test as this increases inflammation so CRP will rise and iron absorption will drop.

Fasting You need to fast for 5 to 12 hours before blood is taken [ideally 9-10 hours]

Iron is an essential mineral but dangerous to the body in large amounts. The body will prevent iron absorption if there is a bacterial infection. Bacterial infections create inflammation which triggers the body to stop iron absorption so if the body detects inflammation it will assume there is a bacterial infection and stop iron absorption e.g. from strenuous exercise, injury. Iron will be moved out of the blood and stored in the liver. Serum iron drops, transferrin saturation drops and ferritin slightly rises because iron is being hidden in the liver.

Serum iron is the least meaningful and least reliable element to measure. Very fickle, moves up and down at different times of day and food intake and drops dramatically when there is inflammation

Haemaglobin reference range only gives a minimum of > 120 (less for Asian and African American women). There is no maximum level but higher is not better! It is very common for menstruating women to have 120-130 and only shift up at menopause. Higher levels are associated with higher mortality 

Transferrin is the taxi for iron [i.e. a marker of shortfall or hunger for iron]

Transferrin is the bodies first response to that individuals shortfall. When a persons is not quite meeting their needs for iron the body responds making the liver produce more transferrin. It is the bodies way of saying I need more iron ie liver sends out more transferrin taxis to pick up more passengers [iron] from the gut.

However this is not true when the body is inflamed by infections, excessive exercise, injuries we can’t say higher transferrin levels mean that you are in need of iron as at this stage the body is stopping absorption and storing away iron in the liver instead.

Pregnancy It is extremely important to have high transferrin to give iron to foetus > 300 – 500

Oestrogens from HRT or contraceptive pill trick the body into thinking there is a baby on board and more iron is needed. So transferrin up regulates so it is now not an indicator that this woman is not meeting her iron needs.

Obese individuals carry an inflammatory load. Transferrin is not an indicator of iron shortfall or iron hunger in obese patients. It is an indicator of iron regulation irregularity.

Transferrin will be quite high although the ferritin is already high. 

Transferrin saturation % is bums on seats ie what % of seats are occupied by iron. 

Transferrin saturation at high levels is possibly iron dumping. Delivering excess of what is needed to organs and tissues or joints, endocrine glands and brain.

Common % Transferrin saturation in menstruating female is 20-25% [seats occupied in the taxi] 30% in men > 45% is too high and may predispose them to haemachromatosis.

35% in woman is not common and if seen consistantly in a fasting state then maybe danger of haemachromatosis (iron overload). Beware of inexplicable joint pain. Iron is commonly dumped in joints.

Ferritin 20-220 is official range but 34-46 is the average ie ideal for menstruating women. Ferritin is a surplus so we don’t want more surplus so don’t go for higher levels.

If you are feeling well, not overly tired, short of breath, dizzy then you are at your ideal ferritin level. Your sweet spot may be only 25 as long as your  Transferrin saturation % is not high so therefore not demanding more uptake.

Someone elses Transferrin saturation % may be 30 or 40 showing a hunger for more iron so this individual needs more.


Taking large doses ie > 20 mg elemental iron is too high a risk for the body. So the gut reduces absorption. 70-90 mg per day will create a shutdown for 48 hours.

Taking 20 mg of iron every 2nd day re Monday, Wednesday, Friday is proven to be the most effective.

Vegans have no excess iron so can have a daily 20 mg dose.

Joint pain consider possible inflammatory causes such as;

Excess exercise
Bacterial and other infections
Excess iron [stop supplementation]