Total IgE Unit Converter
Total IgE Unit Converter
Convert total IgE between kU/L, IU/mL and ng/mL, and see why the number is a poor standalone allergy test.
Total IgE converter
kU/L ⇄ ng/mLTotal IgE 240 kU/L
Units and conversion
- kU/L, IU/mL
- identical units — both express IgE in WHO international units of allergen-binding activity
- 2.4 ng/mL per IU/mL
- a WHO-defined conversion, not one derived from molecular weight — circulating IgE is heterogeneous and has no single meaningful molar mass
Worked example
Total IgE 240 kU/L
240 kU/L = 240 IU/mL — the units are identical
240 × 2.4 = 576 ng/mL
When total IgE helps, and when it doesn't
| Use | Detail |
|---|---|
| Omalizumab dosing | Dose is determined jointly by total IgE and body weight, using the manufacturer’s dosing table |
| ABPA diagnosis | A total IgE above 1000 kU/L is one of the diagnostic criteria for allergic bronchopulmonary aspergillosis |
| Screening for allergy | Poor — a normal result does not exclude atopy. Specific IgE or skin prick testing answers that question |
| Non-allergic causes of a raised result | Parasitic infection, hyper-IgE syndrome, some lymphomas, and smoking |
Why a single IgE number rarely answers the clinical question
Total IgE is reported in kU/L or IU/mL, which are numerically identical because both express the same WHO international unit of allergen-binding activity. Converting to a mass unit uses a WHO-defined factor of 2.4 ng per IU, fixed by international agreement rather than derived from a molecular weight — circulating IgE is heterogeneous, so no single molar mass applies to it. This is also why the analyte carries no molar conversion here.
On its own, total IgE is a poor allergy test in either direction. It is raised in atopic disease but also in parasitic infection, allergic bronchopulmonary aspergillosis, hyper-IgE syndrome, some lymphomas and in smokers, and a normal value does not exclude clinically significant allergy. Where the question is whether a patient is allergic to a specific trigger, specific IgE testing or skin prick testing gives the answer that total IgE cannot.
Total IgE genuinely matters in two other settings. Omalizumab dosing is determined jointly by total IgE and body weight, so the number must be current and accurate before treatment. And in allergic bronchopulmonary aspergillosis, a total IgE above 1000 kU/L is one of the accepted diagnostic criteria, with a falling level used to track treatment response. Reference ranges are also strongly age-dependent, rising from very low cord-blood levels to adult values only by adolescence.
Frequently asked questions
Are kU/L and IU/mL the same for IgE?
Yes, exactly the same — both express IgE in the WHO international unit of allergen-binding activity, so no conversion is needed between them.
How do I convert IgE to ng/mL?
Multiply the value in kU/L or IU/mL by 2.4. This factor is fixed by WHO definition, not derived from a molecular weight, because circulating IgE has no single meaningful molar mass.
Does a normal total IgE rule out allergy?
No. Total IgE is a poor standalone screening test for allergy in either direction. Specific IgE or skin prick testing against the suspected trigger is what answers that question.
What is total IgE actually used for, if not diagnosing allergy?
Two things mainly: calculating the dose of omalizumab, which depends on total IgE and body weight together, and diagnosing allergic bronchopulmonary aspergillosis, where a level above 1000 kU/L is a criterion.
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References
- World Health Organization. International Reference Preparation 75/502 for human immunoglobulin E.
- Agarwal R et al. Allergic bronchopulmonary aspergillosis: review of literature and proposal of new diagnostic and classification criteria. Clin Exp Allergy. 2013;43(8):850–73.