Iron deficiency is the most common nutritional deficiency in the world. It is also one of the most poorly tested. Haemoglobin catches it when it is severe. Ferritin catches it earlier but can be masked by inflammation. Full iron studies tell you the truth.
Most blood tests check haemoglobin (too late) or ferritin (can be misleading). Full iron studies include five markers that together reveal whether you are depleted, overloaded, or genuinely normal.
| Marker | What It Measures | What It Tells You |
|---|---|---|
| Ferritin | Iron stored in your tissues | The primary storage marker. Levels below 30 ug/L indicate depleted stores even if technically "in range." Optimal is 50 to 150 for most people. However, ferritin is also an acute-phase reactant, meaning inflammation, infection, or heavy exercise can falsely elevate it. |
| Serum iron | Iron currently circulating in your blood | Shows how much iron is available for immediate use. Fluctuates throughout the day and with meals. Most useful when interpreted alongside TIBC and transferrin saturation. |
| TIBC | Total iron-binding capacity | Measures the total amount of transferrin available to bind iron. High TIBC means your body is hungry for iron (the transport system is running empty). Low TIBC can indicate iron overload or chronic disease. |
| Transferrin | The protein that transports iron in the blood | Elevated transferrin with low serum iron confirms genuine iron deficiency. Low transferrin can indicate chronic inflammation, liver disease, or iron overload. |
| Transferrin saturation | The percentage of transferrin loaded with iron | The most reliable single marker for functional iron status. Below 16% indicates iron deficiency. Above 45% raises concern for iron overload (haemochromatosis). Not affected by inflammation the way ferritin is. |
TrueVitals includes all five markers in every panel, from Advanced (£269) onwards. Most private blood testing services check ferritin only. Most GP tests check haemoglobin and sometimes ferritin.
This is the single most important thing to understand about iron testing. Ferritin is the standard marker everyone relies on, but it has a critical flaw: it is an acute-phase reactant.
When your body is fighting inflammation, whether from infection, heavy training, chronic stress, autoimmune conditions, or even obesity, ferritin rises as part of the inflammatory response. This happens independently of your actual iron stores.
The result: someone with genuine iron depletion and significant symptoms (fatigue, breathlessness, brain fog, poor recovery) can have a ferritin of 45 ug/L, which looks "normal." But their transferrin saturation is 11%, their TIBC is elevated, and their serum iron is low. They are functionally iron-deficient. The ferritin is being propped up by inflammation, masking the depletion.
Without full iron studies, this pattern is invisible. The person is told their iron is fine. They supplement anyway, it does not help (because the underlying inflammation is sequestering the iron), and nobody understands why.
This is particularly common in athletes (training-induced inflammation), women with endometriosis or PCOS (chronic inflammation), and anyone with elevated hs-CRP. TrueVitals tests hs-CRP alongside full iron studies so your report can identify whether inflammation is distorting your ferritin result.
Most people think about iron testing in terms of deficiency. But iron overload is equally important to detect and significantly more dangerous if missed.
The most common nutritional deficiency globally. Causes fatigue, breathlessness, brain fog, poor exercise tolerance, hair loss, restless legs, and weakened immunity. More common in women (menstrual blood loss), vegetarians/vegans, athletes, and people on PPIs (reduced absorption). Detected by low ferritin, low transferrin saturation (below 16%), elevated TIBC, and eventually low haemoglobin (anaemia).
Key point: Symptoms begin long before anaemia develops. Ferritin below 30 ug/L with a transferrin saturation below 20% warrants attention even if haemoglobin is normal.
Hereditary haemochromatosis affects approximately 1 in 200 people of Northern European descent. The body absorbs too much iron from food, and excess iron deposits in the liver, heart, pancreas, and joints, causing progressive organ damage. It is one of the most common genetic conditions in the UK and one of the most underdiagnosed.
Key point: Transferrin saturation above 45% is the earliest and most sensitive marker. Ferritin rises later as organ iron accumulates. Most GP tests check haemoglobin (irrelevant for overload) or ferritin alone (late marker). Full iron studies with transferrin saturation catch it at the actionable stage.
Menstrual blood loss is the primary driver of iron deficiency in women. Heavy periods accelerate depletion. Testing every 6 to 12 months with full iron studies catches depletion before symptoms become debilitating. Women's health guide.
Iron losses are higher in athletes through sweat, foot-strike haemolysis (runners), GI losses, and inflammation-mediated sequestration. Ferritin alone is unreliable due to training-induced inflammation. Full studies with hs-CRP are essential. Athletes' testing guide.
Non-haem iron from plant sources has lower bioavailability than haem iron from animal products. Without regular monitoring, iron stores can deplete gradually over months. Supplementation should be guided by actual levels, not assumptions.
While deficiency is less common in men, iron overload (haemochromatosis) predominantly presents in men aged 40 to 60 as the body accumulates excess iron over decades. Transferrin saturation is the screening marker. Early detection prevents organ damage. Men's health guide.
Iron deficiency without anaemia is one of the most common treatable causes of fatigue. If your GP checked haemoglobin and said your iron is fine, full iron studies may reveal a different picture. Fatigue testing guide.
Iron requirements increase substantially during pregnancy. Optimising iron stores before conception reduces the risk of iron deficiency anaemia during pregnancy. Ferritin above 50 ug/L with a transferrin saturation above 20% is the target.
Iron status is connected to multiple other health systems. Thyroid function depends on adequate iron for hormone production. Inflammation (hs-CRP) affects ferritin interpretation. Vitamin C enhances iron absorption. B12 and folate are needed alongside iron for healthy red blood cell production. Kidney function (eGFR) influences erythropoietin production which drives red cell production.
A standalone iron test gives you five markers without context. A TrueVitals panel gives you those same five markers alongside thyroid, inflammation, B12, folate, vitamin D, kidney function, and the full blood count. Your AI-powered report identifies whether your iron status is being affected by inflammation, thyroid dysfunction, or nutritional deficiency, and gives you specific supplementation recommendations including form, dose, and timing. See how our reports work.
Full iron studies: ferritin, serum iron, TIBC, transferrin, and transferrin saturation. Haemoglobin alone catches severe anaemia only. Ferritin alone can be falsely elevated by inflammation. TrueVitals includes all five iron markers in every panel from Advanced (£269).
Yes. Ferritin is an acute-phase reactant. Inflammation from exercise, infection, autoimmune conditions, or chronic stress can elevate ferritin regardless of iron stores. Transferrin saturation is more reliable in inflammatory states. TrueVitals tests hs-CRP alongside iron studies so your report can flag when inflammation may be distorting ferritin.
Most labs use a reference range of 10 to 300 ug/L. Optimal for most adults is 50 to 150 ug/L. Below 30 ug/L indicates depleted stores even if technically "in range." Above 200 ug/L in men or above 150 ug/L in pre-menopausal women warrants investigation for iron overload, especially if transferrin saturation is also elevated.
Hereditary haemochromatosis is a genetic condition where the body absorbs too much iron, depositing it in the liver, heart, pancreas, and joints. It affects approximately 1 in 200 people of Northern European descent. Transferrin saturation above 45% is the earliest marker. Early detection and regular phlebotomy (blood removal) prevents organ damage. Full iron studies catch it; haemoglobin and ferritin-only tests miss it.
Only if your iron studies confirm deficiency. Supplementing without testing risks iron overload, which is dangerous. If deficient, iron bisglycinate is generally the best-tolerated form, taken every other day for optimal absorption. Your TrueVitals report provides specific supplementation recommendations based on your actual levels, including form, dose, and timing.
Ferritin, serum iron, TIBC, transferrin, and transferrin saturation. Plus hs-CRP to flag inflammatory masking. From £269.
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