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Calculator · health

Ivig Dose Calculator

Calculate total IVIG dose in grams by patient weight and clinical indication, with optional ideal body weight adjustment for obese patients.

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Inputs

Patient Weight

Patient Height (for IBW calculation)

Sex

Clinical Indication

Dose per kg

Use Adjusted Body Weight (for obesity)

Total IVIG Dose

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Total IVIG Dose—g

The formula

How the
result is
computed.

What Is IVIG and Why Does Dosing Accuracy Matter?

Intravenous immunoglobulin (IVIG) is a blood-derived therapy composed of pooled IgG antibodies collected from thousands of healthy donors. Clinicians prescribe IVIG for a broad spectrum of conditions including primary immunodeficiency diseases (PID), immune thrombocytopenic purpura (ITP), Kawasaki disease, Guillain-Barré syndrome (GBS), and chronic inflammatory demyelinating polyneuropathy (CIDP). Accurate dose calculation is clinically essential: underdosing results in inadequate immune protection or insufficient immunomodulation, while overdosing raises the risk of adverse effects including headache, aseptic meningitis, acute renal impairment, and thromboembolic events such as deep vein thrombosis or stroke.

The IVIG Dose Formula

The total IVIG dose is calculated using a straightforward weight-based formula:

Dose (g) = [Weight (kg) × Dose (mg/kg)] ÷ 1,000

Dividing by 1,000 converts milligrams to grams, the standard dispensing and labeling unit for commercial IVIG products. For example, a 70 kg patient prescribed 400 mg/kg for PID replacement therapy requires: (70 × 400) ÷ 1,000 = 28 g of IVIG per infusion cycle.

Understanding Each Input Variable

Patient Weight (kg)

Actual body weight (ABW) in kilograms serves as the default dosing weight. For patients at or near their ideal body weight, ABW provides a reliable dosing basis. In obese patients, however, excess adipose tissue does not proportionally increase the immunoglobulin volume of distribution, meaning ABW-based dosing can produce supratherapeutic levels and increase adverse event risk.

Ideal Body Weight and the Devine Formula

When height and sex are entered, the calculator computes ideal body weight (IBW) using the clinically validated Devine formula:

Males: IBW (kg) = 50 + 2.3 × [Height (in) - 60]
Females: IBW (kg) = 45.5 + 2.3 × [Height (in) - 60]

Height entered in centimeters is automatically converted to inches by dividing by 2.54. When actual body weight exceeds IBW, the calculator applies an adjusted body weight (AdjBW) correction: AdjBW = IBW + 0.4 × (ABW - IBW). The 0.4 factor reflects that approximately 40% of excess adipose mass participates in immunoglobulin distribution, a pharmacokinetic principle consistent with established clinical dosing guidance.

Clinical Indication and Standard Dose Ranges

The prescribed dose per kilogram varies substantially by clinical indication. Evidence-based dose ranges include:

PID Replacement: 300-600 mg/kg every 3-4 weeks, titrated to trough IgG above 500-700 mg/dL
ITP Treatment: 1,000 mg/kg/day for 1-2 days, or 400 mg/kg/day for 5 days
Kawasaki Disease: 2,000 mg/kg as a single infusion within the first 10 days of illness
GBS: 400 mg/kg/day for 5 days (total cumulative dose: 2,000 mg/kg)
CIDP Maintenance: 1,000 mg/kg every 3 weeks, or 500 mg/kg every 1-2 weeks

Worked Clinical Example with IBW Adjustment

A 90 kg male patient (height 175 cm) is admitted with GBS and prescribed IVIG 400 mg/kg/day for 5 days. Step 1 — convert height: 175 ÷ 2.54 = 68.9 in. Step 2 — compute IBW: 50 + 2.3 × (68.9 - 60) = 70.5 kg. Step 3 — since ABW (90 kg) exceeds IBW, compute AdjBW: 70.5 + 0.4 × (90 - 70.5) = 78.3 kg. Step 4 — daily dose: (78.3 × 400) ÷ 1,000 = 31.3 g/day. Step 5 — total 5-day course: 31.3 × 5 = 156.5 g. Without IBW adjustment, the raw ABW-based dose would have been 180 g — a 15% overestimate.

Methodology and Authoritative Sources

Dose ranges in this calculator are derived from peer-reviewed clinical evidence and regulatory labeling. The XEMBIFY Package Insert (FDA) specifies PID replacement dosing of 300-600 mg/kg every 3-4 weeks with dose individualization based on trough IgG levels. Detailed immunoglobulin dose calculation methodology is described in Bonilla et al., Calculating the Dose of Subcutaneous Immunoglobulin for Primary Immunodeficiency (PMC, 2012). Neuromuscular dosing protocols align with the American Academy of Neurology (AAN) Guidelines for IVIG in Neuromuscular Disorders. The Devine IBW formula and adjusted body weight correction reflect established clinical pharmacokinetic principles widely adopted in hospital pharmacy practice. This calculator is intended to support — not replace — clinical judgment, and all IVIG orders should be verified by a licensed pharmacist or physician.

Reference

Frequently asked questions

What is the standard IVIG dose for primary immunodeficiency (PID)?

The standard IVIG replacement dose for primary immunodeficiency is 300-600 mg/kg administered intravenously every 3-4 weeks. The specific dose is titrated based on the patient's trough IgG level, with a target trough above 500-700 mg/dL. Starting doses are typically 400-600 mg/kg, and adjustments are made at each subsequent infusion based on measured serum IgG troughs and clinical response, including infection frequency. Per the FDA-approved XEMBIFY labeling, doses may be fully individualized for each patient's clinical status.

How does the IVIG dose calculator handle obese patients?

For obese patients, the calculator applies adjusted body weight (AdjBW) rather than actual body weight to prevent supratherapeutic dosing. AdjBW is computed as: IBW + 0.4 × (actual weight - IBW), where IBW comes from the Devine formula. The 0.4 correction factor reflects that roughly 40% of excess adipose mass contributes to immunoglobulin distribution volume. Enabling the adjusted body weight option and entering height and sex allows the calculator to apply this correction automatically whenever actual weight exceeds ideal body weight.

What IVIG dose is recommended for immune thrombocytopenic purpura (ITP)?

For immune thrombocytopenic purpura, two evidence-based IVIG regimens are standard: 1,000 mg/kg/day for 1-2 consecutive days, or 400 mg/kg/day for 5 days. Both deliver a total cumulative dose of approximately 2,000 mg/kg. For a 70 kg patient, the 2-day high-dose regimen requires 70 g/day, totaling 140 g. The high-dose 2-day schedule is preferred in acute bleeding situations where rapid platelet count elevation — typically seen within 24-72 hours — is clinically urgent.

How is ideal body weight calculated for IVIG dosing?

Ideal body weight for IVIG dosing uses the Devine formula. For males: IBW (kg) = 50 + 2.3 × (height in inches - 60). For females: IBW (kg) = 45.5 + 2.3 × (height in inches - 60). Height entered in centimeters is divided by 2.54 to convert to inches. For example, a 175 cm male has an IBW of approximately 70.5 kg. For patients shorter than 60 inches (152 cm), the formula yields a subtraction from the base weight, and clinical pharmacist review is recommended for patients of very short stature.

What is the total IVIG dose for Guillain-Barré syndrome (GBS)?

The standard IVIG course for Guillain-Barré syndrome is 400 mg/kg/day administered for 5 consecutive days, delivering a total cumulative dose of 2,000 mg/kg. For a 70 kg patient, this equals 28 g per day and 140 g over the full course. According to AAN guidelines for IVIG in neuromuscular disorders, this 5-day regimen demonstrates equivalent efficacy to plasmapheresis for GBS and is the preferred treatment for patients who cannot tolerate plasma exchange. Obese patients should have IBW adjustment considered to avoid toxicity.

What are the clinical risks of incorrect IVIG dosing?

Incorrect IVIG dosing carries measurable clinical risks in both directions. Underdosing in PID patients results in inadequate IgG trough levels, leaving patients vulnerable to recurrent sinopulmonary bacterial infections. Overdosing increases exposure to serious adverse effects including aseptic meningitis, acute tubular necrosis (especially with sucrose-stabilized formulations), hemolytic anemia, and thromboembolic complications such as stroke or pulmonary embolism. Because adverse event risk is dose-dependent, precise weight-based calculation — with IBW adjustment in obese patients — and mandatory pharmacist verification of all IVIG orders are strongly recommended in clinical practice.