Weight-Based Dosing Errors: Pediatric Medication Review (Free Tool)
Most pediatric doses, and many adult doses of high-alert drugs, are ordered per kilogram. That single step, multiplying a reference figure by the patient's weight, is where a large share of serious medication errors begin. The weight is wrong, the units are wrong, a decimal point moves, a per-day total is given as one dose, or the dose for one route is pushed by another. The result on the medication administration record (MAR) often looks ordinary: a number, a time, initials. Finding the error means recomputing it. This post explains how weight-based dosing errors happen, how to check a MAR against a published reference range, which drugs deserve the first look, and which records show where the chain of checks failed.
How weight-based dosing errors happen
The reference table behind the dose checker annotates recognized error patterns drug by drug. Grouped, they fall into seven categories.
1. The wrong weight
The dose was calculated correctly against a weight that was not the patient's. Common sources: an estimated or stated weight never replaced by a scale weight, a stale admission weight on a long stay, a sibling's or prior patient's weight carried in the system, or a dosing weight (ideal or adjusted body weight, used for some drugs in obesity) applied where actual body weight was intended, or the reverse. The tool's own instruction is to use the weight documented at the time of the order, not an estimate.
2. Pounds entered as kilograms
A weight recorded in pounds and entered into a kilogram field inflates every weight-based dose by a factor of about 2.2. The error is invisible on the MAR because the mg/kg figure the system displays is "correct" against the wrong weight. It is caught only by going back to the scale reading and its units.
3. Decimal-point and tenfold errors
A misplaced decimal, a trailing zero (5.0 read as 50), or a missing leading zero (.5 read as 5) produces a tenfold dose. The checker flags a dose that lands at roughly ten times or one-tenth of the reference as a suspected decimal error. In cardiac arrest, the endotracheal epinephrine dose (0.1 mg/kg) is ten times the IV dose (0.01 mg/kg), so the same number can be right by one route and tenfold by another.
4. Unit confusion
Several drugs in the table carry a unit warning. Fentanyl is dosed in micrograms; a dose written in milligrams that is 1,000 times the expected dose is a recognized pattern. Heparin and insulin are dosed in units, not milligrams. Fosphenytoin and phenytoin loading doses are expressed in phenytoin equivalents (mg PE). Magnesium sulfate errors include grams-versus-milligrams and mEq-versus-mg confusion, compounded by the fact that pediatric arrest dosing (25 to 50 mg/kg, maximum 2 g) and adult obstetric dosing (4 to 6 g load) live on very different scales.
5. Concentration mix-ups
The right mg/kg dose drawn from the wrong vial. The table notes epinephrine 1 mg/mL versus 0.1 mg/mL (IM anaphylaxis dosing uses the 1 mg/mL product; IV arrest dosing uses 0.1 mg/mL), heparin 10 units/mL versus 10,000 units/mL as a recognized pediatric pattern, and the conversion traps in local anesthetics (lidocaine 1 percent is 10 mg/mL, 2 percent is 20 mg/mL; bupivacaine 0.25 percent is 2.5 mg/mL).
6. Wrong interval or basis
Many references give a per-day figure divided into doses (amoxicillin 20 to 45 mg/kg/day divided every 8 or 12 hours; cephalexin 25 to 100 mg/kg/day). If the per-day total is written as a single dose, or a "divided every 6 hours" regimen is given every 4 hours, the per-dose figure may look fine while the daily total runs far above the maximum. Acetaminophen is the classic example: 10 to 15 mg/kg per dose is within range, but the daily cap (75 mg/kg/day orally, with absolute daily maxima) and the five-doses-in-24-hours limit are where cumulative toxicity hides, especially when combination products containing acetaminophen are not counted toward the total.
7. Wrong route, wrong population, wrong drug
Midazolam oral syrup dosing (0.25 to 0.5 mg/kg) is several times the IV sedation dose; ketamine IM dosing (6.5 to 13 mg/kg) is several times the IV dose; a fixed adult dose given to a child under the weight threshold; and look-alike opioids, where hydromorphone is roughly 5 to 7 times as potent as morphine by weight and the two are a recognized confusion pair.
How to check a MAR against a reference range
- Fix the weight. Find the weight documented at the time of the order, its units, its source (scale, stated, estimated) and who entered it. If the record has more than one weight, note all of them and which one the order system used.
- Fix the dose actually given. Use the MAR or eMAR entry, not the order, and note the unit (mg, mcg, g, units, mg PE). For an infusion, use the amount per hour.
- Compute mg/kg per dose (dose divided by weight in kg) and mg/kg/day (per-dose figure times the number of doses in 24 hours from the frequency on the MAR).
- Pick the right row. Population (pediatric or adult; the table does not cover neonates under one month), route and indication all change the range. The ampicillin range is wide (25 to 200 mg/kg/day) because it spans soft-tissue infection to meningitis; the indication in the order decides which end applies.
- Compare against four limits: the per-dose range, the per-day maximum, the absolute single-dose maximum and the absolute daily maximum. A dose can pass one and fail another.
- Ask whether the deviation was intentional. Level-guided vancomycin, extended-interval aminoglycosides, high-dose amoxicillin for otitis media, a status epilepticus loading dose of levetiracetam (60 mg/kg, far above maintenance) and pulse-dose steroids are all documented regimens that sit outside the general row. The pharmacy kinetics notes and the order's indication are where that answer lives.
- Trace the chain. An out-of-range dose that was ordered, verified by pharmacy, dispensed and administered passed several checks. The records below show which check failed and who documented what.
High-alert drugs in the reference table
The table marks the drugs ISMP treats as high-alert, meaning an error carries a heightened risk of serious harm. These deserve the first pass in any medication review.
| Class | Drugs flagged high-alert in the table | Error pattern noted |
|---|---|---|
| Opioids | Morphine, hydromorphone, fentanyl | Morphine-hydromorphone confusion; fentanyl mg-for-mcg (1,000-fold); tolerance and sedation monitoring change the analysis |
| Anticoagulants | Heparin, enoxaparin | Units not mg; 10 vs 10,000 units/mL vials; prophylaxis order dosed at treatment 1 mg/kg, or treatment order at a fixed 40 mg |
| Insulin | Regular insulin IV infusion (DKA) | Units; a bolus in a child with DKA is contrary to the ISPAD guideline |
| Sedatives and anesthetics | Midazolam, lorazepam, diazepam, propofol, ketamine | Oral vs IV midazolam dose; IM vs IV ketamine; concurrent opioids lower the required dose |
| Neuromuscular blockers | Succinylcholine, rocuronium | Succinylcholine boxed warning in children with undiagnosed myopathy |
| Cardiac and resuscitation | Epinephrine (IM and IV), adenosine, amiodarone, magnesium sulfate | Epinephrine concentration and route; ET dose ten times IV; grams vs mg and mEq vs mg for magnesium |
| Local anesthetic | Bupivacaine (epidural) | 0.75 percent contraindicated for obstetric epidural; mg/mL conversion |
| Monitored antibiotic | Vancomycin (ISMP monitoring) | Level-guided adjustments can look out of range; pull the pharmacy kinetics notes |
Check the dose per kilogram in a minute
Enter the drug, the weight (kg or lb), the dose given, the route and the frequency. Get mg/kg per dose and mg/kg/day, the cited reference range, a flag if the dose is outside it or looks like a decimal error, and the records to request. Free, no login, math only.
Open the Weight-Based Dose Checker →A worked example (hypothetical)
The facts below are invented for illustration. No real patient, clinician or case is described.
The patient is a four-year-old seen in an emergency department for fever. The triage sheet records a weight of 40 lb. The order entry screen shows a weight of 40 kg. An order is placed for oral acetaminophen 600 mg every six hours, which the system calculated as 15 mg/kg against the 40 kg figure. Pharmacy verified it, the MAR shows four doses given over 24 hours, and the child was later found to have liver injury.
Recomputed against the actual weight: 40 lb is about 18.1 kg. Entered into the checker with the weight in pounds, the dose of 600 mg works out to roughly 33 mg/kg per dose and about 132 mg/kg/day. The pediatric oral row (WHO Model Formulary for Children) gives 10 to 15 mg/kg per dose, every 4 to 6 hours, no more than 5 doses in 24 hours, with a 75 mg/kg/day maximum. The dose is flagged above range on both the per-dose and per-day basis. The checker's output is a comparison and a flag, nothing more; the explanation is in the records.
Those records tell the story: the weight documentation shows a pounds reading entered into a kilogram field; the order shows the weight the system used; the pharmacy verification log shows whether a dose-range alert fired and, if so, the override reason; the MAR shows the dose was given four times. Each is a different defendant's conduct and a different deposition. For the defense, the same records may show the alert did fire, was overridden with a documented rationale, or that a second weight was obtained and the error corrected before the third dose.
What to request next
- The original order (CPOE record or paper order) with the ordering provider, time, dose, units, route, frequency and the weight the system used for any dose calculation.
- The weight documentation at the time of the order: admission weight, the scale or stated or estimated source, units, who entered it and when it was last updated.
- The pharmacy verification log: verifying pharmacist, time, any dose-range alert that fired, the override reason, and the pharmacy's weight and dosing-weight fields.
- MAR or eMAR entries for every administration, with the barcode scan record, the dose actually documented and the nurse's independent double-check if the policy requires one.
- Smart-pump or infusion-pump logs (programmed concentration, rate, dose and any library alerts or overrides) for infusions.
- Automated dispensing cabinet transactions and compounding records for the product and concentration actually used.
- The dose-range checking configuration and alert history in the EHR and pharmacy system for this drug.
- Facility policies on weight-based dosing, pediatric dosing limits, high-alert medications and independent double checks in force on the date.
- The incident report, the pharmacy medication-error report and any root-cause analysis for the event, where discoverable.
What the tool does not do
The checker does arithmetic against a published range and reports the result. It carries the same limits the tool states on its own page:
This is a chart-review aid, not clinical guidance. The reference ranges are starting points compiled from the public sources cited on each row. Dosing varies by indication, age band, renal and hepatic function, prior exposure, institutional protocol and the specific product. A dose outside the range here is a question for a pharmacist or physician expert, not a conclusion. A dose inside the range does not mean it was correct for this patient.
It does not cover neonates under one month. It does not know the indication, the renal function, the prior opioid exposure or the institution's protocol unless the reviewer brings them from the chart. It does not decide whether a deviation was clinically significant, intentional (level-guided, renal adjustment, tolerance) or an error, and it does not say whether the dose caused the injury. Labels and guidelines are revised; verify the range against the cited source and the product actually used before it goes into a memo or expert packet. Pharmacist verification of the dose, the product and the indication is the step the tool is designed to lead into, not replace.
Next step: organize the whole medication record
Upload the chart and get a Bates-cited chronology that pins every order, MAR entry, pharmacy note and weight entry to its page, so the dosing timeline is ready for the expert.
Upload the chart →Frequently asked questions
How do I check whether a pediatric dose on the MAR was correct?
Find the weight documented at the time of the order, in kilograms, and confirm its source. Divide the dose administered by that weight to get mg/kg per dose; multiply by the number of doses a day for mg/kg/day. Compare both against the published range for the drug, population, route and indication in the record, and against any absolute maximum. Then look at the chain: the order, the pharmacy verification, the dispensing record and the MAR, to see where a wrong number entered and which check failed.
What are the most common ways weight-based dosing goes wrong?
A wrong or stale weight, including a weight in pounds entered as kilograms (a 2.2-fold overdose); decimal-point errors that produce a tenfold dose; milligram-microgram confusion with drugs such as fentanyl; grams-milligrams and mEq-mg confusion with magnesium; concentration mix-ups such as epinephrine 1 mg/mL versus 0.1 mg/mL or heparin 10 versus 10,000 units/mL; a per-day total given as a single dose or the wrong interval; the wrong route's dose given by another route; and an adult or fixed dose given to a child.
What does the free Weight-Based Dose Checker actually do?
You enter the drug, the patient's weight in kg or lb, the dose documented as given, the route, the frequency and the age group. It computes mg/kg per dose and mg/kg/day, shows the published reference range for that drug and population from a cited public source (FDA label via DailyMed, WHO Model Formulary for Children, AHA PALS/ACLS 2020, AES 2016, CHEST 2012, ASHP/IDSA 2020, ISPAD 2022), flags a dose outside the range or one that looks like a decimal-point error, and lists the records to request. The math runs in the browser; only the drug name and the outcome category are logged. It is a chart-review aid, not clinical guidance.
Does a dose outside the reference range prove negligence?
No. The reference ranges are starting points compiled from cited public sources and dosing varies by indication, age band, renal and hepatic function, prior exposure, institutional protocol and the specific product. Some out-of-range doses are intentional: high-dose amoxicillin for otitis media, level-guided vancomycin, extended-interval gentamicin, or a status epilepticus loading dose. A dose outside the range is a question for a pharmacist or physician expert, not a conclusion, and a dose inside the range does not mean it was correct for this patient.
Related: pediatric medication dosing errors in malpractice cases and the five rights and MAR review.