Lidocaine's maximum safe dose depends on two things at once: body weight, and whether epinephrine is present. This calculator applies both the standard weight-based formula and the absolute ceiling that caps it, then converts that dose into a practical volume for the concentration you're using.
Why there are two different ceilings
Plain lidocaine (without epinephrine) carries a standard reference ceiling of 4.5 mg/kg of body weight, up to an absolute maximum of 300 mg. Adding epinephrine raises the ceiling to 7 mg/kg, up to an absolute maximum of 500 mg. Epinephrine's vasoconstriction narrows blood vessels at the injection site, which slows the rate lidocaine enters the systemic circulation — that slower absorption is what allows a higher total dose to stay within the same safety margin.
These figures are drawn from FDA lidocaine labeling as summarized in standard clinical references (StatPearls, the Iowa Head and Neck Protocols) and are widely used across anesthesia, dermatology, dentistry, and emergency medicine.
Why the absolute ceiling matters, not just the mg/kg math
A purely linear mg/kg formula would keep scaling the max dose up indefinitely for heavier patients. In practice, both the plain and with-epinephrine formulas are capped at a fixed absolute ceiling — 300 mg and 500 mg respectively — because doses above that level carry meaningfully higher toxicity risk regardless of weight. This calculator always displays the lower of the two: the weight-based math, or the absolute ceiling, and tells you which one is binding for your inputs.
From max dose to max volume
A max dose in milligrams isn't directly useful at the bedside — you need to know how many milliliters of your specific concentration that corresponds to. Lidocaine concentration is expressed as a percentage (grams per 100 mL), so a 1% solution is 10 mg/mL and a 2% solution is 20 mg/mL. Dividing the max dose by the mg/mL of your concentration gives the maximum volume you can safely draw up.
Limits and edge cases
This calculator applies the standard reference formula and ceiling arithmetic only. It does not account for the patient's specific comorbidities (hepatic impairment, cardiac conduction disease), the injection site's vascularity, total anesthetic load from multiple sources or repeat dosing, pediatric-specific dosing (which uses different references), or drug interactions. Always verify the dose against current prescribing information and institutional protocol, and review the LAST Warning tab for signs of Local Anesthetic Systemic Toxicity before administering.