Drug Half Life Calculator
Our drug halflife calculator is an easy tool to discover the dosage of a drug that is still present in a patient's system. The halflife of a drug describes the process of its elimination.
Read on to discover the halflife of a drug and how to calculate the halflife of a medication. We'll also present plenty of useful examples.
This form of half life is not to be mistaken with the decay of radioactive elements! ☢️
How to use the drug halflife calculator?
In order to use our 1/2 life calculator you'll need the following data:

The half time of a given drug  this input can be either in minutes, hours, or days. The calculator will set the unit of the result automatically.
If you don't know the half life of the drug, take a look at our .

Dosage  the amount of the drug administered at the very start.

Your results will be shown in a table that consists of at least 5 halflife cycles:

Time  the amount of time that has passed since the first administration of a drug;

Dosage  the amount of drug left in the patient's body at the given time; and

Concentration  the part of the original concentration still present in the patient's body.

What is the halflife of a drug?
In pharmacology, when we talk about the half life of a drug we usually mean the time it takes a drug's concentration in the blood plasma to reduce by half.
💡 The half life of a drug describes the amount of time it will take half of the administered drug to be eliminated. 
Why do we need it?
The halflife of a drug helps us assess the potency and toxicity of a drug over a given amount of time. If we know the elimination time, we can easily evaluate how often the drug should be administered to maximize its effect and minimize its adverse reactions.
The concentration of a drug at a given moment crucial in drugs with narrow tolerance range, e.g., medicines that can prolong the patient's QT and consequently lead to heart arrhytmias.
🕒 The half life of a drug is the complete opposite of its doubling time.
How to calculate a halflife of a drug?
Our drug elimination half life calculator uses the following equation:
Dosage(t) = Dosage(0) * 0.5^{(t/T)}
Where:
 T  the half life of a drug;
 t  time that has passed since the first, original administration of the drug;
 Dosage(t)  the amount of drug present in a patient's body after time t; and
 Dosage(0)  the amount of drug administered at the very beginning.
Halflife of medication  examples
Don't know the halflife of a given drug? Are you looking for an Adderall halflife calculator, or any other specific drug calculations? We're here to help!
Drug  Half time 
Acetaminophen  14 h 
Adderall  914 h 
Amiodarone  26  107 days 
Carbamazepine  14  47 h 
Ciprofloxacin  4 h 
Diazepam  2137 h 
Digoxin  3648 h 
[Epinephrine](calc:2393)  23 min 
Fentanyl  312 h 
Fluconazole  2050 h 
Ganciclovir  36 h 
Haloperidol  1441 h 
Heparin  36 h 
Ketoconazole  28 h 
Lidocaine  12 h 
Methotrexate  310 h 
Metronidazole  8 h 
[Morphine](calc:1129)  17 h 
Oxycodone  35 h 
Phenobarbital  81117 h 
Propranolol  26 h 
Streptomycin  56 h 
Tetracycline  711 h 
Valproic Acid  916 h 
Warfarin  2060 h 
Time (min)  Dosage (mg)  Concentration 

    50% 
    25% 
    12.5% 
    6.25% 
    3.125% 
    1.562% 