IVIG Dose Calculator
Calculate IVIG immunoglobulin dose from ideal or adjusted body weight and RhIG vials for maternal hemorrhage.
What Is IVIG?
Intravenous immunoglobulin (IVIG) is a blood product rich in antibodies used to treat primary immunodeficiency, autoimmune conditions such as Guillain–Barré syndrome, Kawasaki disease, and selected hematologic disorders. Dosing is usually expressed in grams per kilogram of body weight, but the weight used for calculation depends on ideal, actual, or adjusted body weight.
How IVIG Dose Is Calculated
This calculator uses the Devine ideal body weight formula. For men, ideal weight equals 50 kg plus 2.3 kg for each inch over 5 feet; for women, 45.5 kg plus 2.3 kg per inch over 5 feet. If the patient's actual weight is lower than ideal weight, actual weight is used. For obese patients with BMI of 30 or higher, adjusted body weight is used: ideal weight plus half the difference between actual and ideal weight. The IVIG dose in grams equals the prescribed dosing rate (g/kg) multiplied by the selected dosing weight.
RhIG Dose for Maternal Hemorrhage
Rh(D) immune globulin (RhIG) prevents hemolytic disease of the fetus and newborn when an Rh-negative mother is exposed to Rh-positive fetal red blood cells. After a bleed, clinicians estimate maternal blood volume with Nadler's formula and combine it with the percentage of fetal cells in the maternal circulation (from flow cytometry or Kleihauer-Betke testing) to estimate how many standard 30 mL RhIG vials are required.
Frequently Asked Questions
Which weight should be used for IVIG dosing?
Use Devine ideal body weight for most patients. If actual weight is below ideal, use actual weight. For obesity (BMI ≥ 30), use adjusted body weight: ideal weight plus 0.5 × (actual − ideal).
What is a typical IVIG dosing rate?
Common maintenance regimens range from 0.4 to 0.8 g/kg per infusion, but the exact rate depends on the indication, product, and prescribing protocol. Always follow institutional guidelines and specialist orders.
Why does sex affect ideal body weight?
The Devine formula uses different baseline weights for men (50 kg) and women (45.5 kg) at 5 feet tall, reflecting population averages used in clinical dosing references.
How is maternal blood volume estimated for RhIG?
This tool uses Nadler's formula for women: 356.1 × height (m)³ + 33.08 × weight (kg) + 183.3, giving blood volume in milliliters. Height and weight should reflect the mother's measurements at the time of assessment.
What does the fetal cells percentage mean?
It is the proportion of fetal red blood cells detected in the mother's blood sample, usually reported as a percentage from Kleihauer-Betke staining or flow cytometry after a suspected fetomaternal hemorrhage.
Can this calculator replace medical advice?
No. IVIG and RhIG dosing require clinical judgment, laboratory confirmation, and local protocols. Use this calculator for education and estimation only, and confirm all doses with a qualified healthcare provider.
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