What is the Rumack-Matthew nomogram?

It is a graph plotting serum acetaminophen concentration versus time after a known acute single ingestion. This page uses the 150-line as reference context, not as a substitute for toxicology review.

What is the toxic dose of acetaminophen?

For acute single ingestion, ≥150 mg/kg is the classic worksheet trigger for possible toxicity. Higher doses raise concern, but Complete View still depends on timing, labs, and toxicology review.

Does this page decide NAC treatment?

No. It shows dose and timing context only. Treatment decisions belong in a live poison-center, toxicology, or emergency-care pathway.

Why is the 4-hour serum level important?

Acetaminophen absorption usually peaks within about 1 to 4 hours for immediate-release products. Earlier levels can look falsely reassuring.

Tylenol Overdose Calculator

Review acetaminophen overdose dose severity, Rumack-Matthew nomogram thresholds, and liver-injury context in one worksheet.

🚨 Emergency reference: Suspected acetaminophen overdose needs real-time Poison Control (1-800-222-1222) or emergency evaluation. This page is a worksheet for dose, timing, and nomogram context only.

Body Weight

Total APAP Ingested

Ingestion Type

Hours Since Ingestion

hours

Serum APAP Level (if available)

µg/mL

AST/ALT (if available)

U/L

INR (if available)

Ingested Dose Severity

<75 mg/kg Low

75–149 Borderline

150–249 Potentially toxic

250–499 High

≥500 Massive

Dose in mg/kg

142.9 mg/kg

Intermediate range — interpret with serum level and timing

Worksheet Trigger Context

Entered values do not cross the common worksheet trigger

This page still does not replace poison-center guidance

Early Decontamination Context

Short time-window discussion still exists

Activated charcoal decisions depend on timing, airway protection, and the full presentation

Rumack-Matthew Reference Line

Reference line at 4h = 150 µg/mL

Use this only for acute single ingestions with a known time and a 4–24 hour serum level

Liver Injury Context

No entered lab abnormality

Enter AST/ALT and INR if you want lab context alongside the dose worksheet

Rumack-Matthew Nomogram Reference Line

Hours Post-Ingestion	Reference Line (µg/mL)	Your Level	Context
4h	150 µg/mL	—	—
5h	120 µg/mL	—	—
6h	100 µg/mL	—	—
7h	80 µg/mL	—	—
8h	67 µg/mL	—	—
10h	45 µg/mL	—	—
12h	30 µg/mL	—	—
14h	20 µg/mL	—	—
16h	13 µg/mL	—	—
18h	10 µg/mL	—	—
20h	7 µg/mL	—	—
24h	4 µg/mL	—	—

Typical Timeline of Acetaminophen Toxicity

Stage	Time	Symptoms	Labs
I	0–24 hours	Nausea, vomiting, malaise, diaphoresis (may be asymptomatic)	Normal or slightly elevated AST
II	24–72 hours	Symptoms may improve while RUQ pain appears	Rising AST/ALT, PT/INR, bilirubin
III	72–96 hours	Peak hepatotoxicity, coagulopathy, encephalopathy, renal failure	AST can exceed 10,000; INR may peak
IV	4–14 days	Recovery or progressive multi-organ failure depending on severity	Labs normalize over time if recovery occurs

Planning notes, formulas, and examples

About the Tylenol Overdose Calculator

The Tylenol Overdose Calculator is an acetaminophen overdose worksheet that brings together dose-per-kilogram context, Rumack-Matthew nomogram thresholds, and basic liver-injury context. Acetaminophen overdose is a major cause of acute liver failure, so the value of a page like this is not to replace Poison Control or emergency evaluation, but to help organize the key numbers that are often reviewed early.

The Rumack-Matthew nomogram is the classic reference for acute single-ingestion assessment. It plots serum acetaminophen concentration against time since ingestion and shows whether the entered level sits above or below the 150 µg/mL reference line. However, the nomogram has important limits: it is not valid for repeated supratherapeutic ingestion, unknown timing, most extended-release scenarios, or levels drawn before 4 hours.

This calculator therefore works best as a timing-and-dose worksheet. It is not a stand-alone toxicology workflow or treatment protocol.

When This Page Helps

Acetaminophen overdose review usually turns on a few linked numbers: how much was taken, when it was taken, and where the serum level sits relative to the nomogram. This calculator keeps those numbers together so the page works as a quick worksheet during a toxicology review.

How to Use the Inputs

Enter the patient body weight in kilograms.
Enter the total amount of acetaminophen ingested in mg.
Select the ingestion type.
Enter hours since ingestion for nomogram context.
Enter serum APAP level if available.
Optional: enter AST/ALT and INR for liver-injury context.
Use the result as a worksheet and contact Poison Control or emergency services for real-time management.

Formula used

Dose worksheet trigger: ≥150 mg/kg (acute single ingestion)
Rumack-Matthew reference line: 150 µg/mL at 4 hours → about 4.7 µg/mL at 24 hours (semi-logarithmic)
Nomogram use setting: acute single ingestion, known time, 4–24 hour level

Example Calculation

Result: 200 mg/kg — above common worksheet trigger; serum 180 µg/mL is above the 4-hour reference line

A 70 kg patient ingesting 14,000 mg (14 g) of acetaminophen equals 200 mg/kg, which is above the classic 150 mg/kg worksheet trigger. At 4 hours post-ingestion, a serum level of 180 µg/mL also sits above the 150-line reference value of 150 µg/mL.

Tips & Best Practices

Use the nomogram only for acute single ingestions with a known time and a level drawn 4–24 hours after ingestion.
Unknown timing, repeated supratherapeutic ingestion, and extended-release products need broader review than a single nomogram point.
Dose thresholds are useful reference points, not stand-alone management decisions.
If overdose is suspected, live Poison Control guidance matters more than any static worksheet.

The Rumack-Matthew Nomogram

The Rumack-Matthew nomogram gave clinicians an objective frame for acute acetaminophen overdose review. In practice, the 150-line is commonly used as a reference line in many systems.

Limits of the Worksheet

The nomogram is a timing-specific tool. Delayed absorption, extended-release products, unknown time of ingestion, and repeated supratherapeutic exposure all make a simple point-on-the-line interpretation much less reliable.

Best Use

This page is most useful for organizing dose, timing, and serum-level context before or during a real toxicology discussion. It should not be treated as a stand-alone antidote or decontamination protocol.

Sources & Methodology

Last updated: March 28, 2026

Methodology

This worksheet organizes acute acetaminophen ingestion timing, dose-per-kg context, and Rumack-Matthew reference thresholds. It is a review aid, not a treatment protocol.

Sources

Rumack-Matthew nomogram reference materials (Clinical toxicology)
Poison Control acetaminophen overdose guidance (Poison Control)
NIH LiverTox: Acetaminophen (NIH/NIDDK)

Frequently Asked Questions

It is a graph plotting serum acetaminophen concentration versus time after a known acute single ingestion. This page uses the 150-line as reference context, not as a substitute for toxicology review.