The dose for this patient, not the textbook one
Drug dosage calculator app for doctors, NPs and PAs with renal, hepatic and weight-based dosing
A calculator app gives you a creatinine clearance. A drug reference gives you a renal adjustment table. Joining the two, for this drug and this patient, is still your job at 6 pm with a full waiting room.
Prescriber.io takes the patient once and flags the dose adjustment for the drug you are about to prescribe, with the threshold and the source.
Press Run check for the interaction, contraindication, dosing and alternatives on this pair.
Not matched, so not checked: .
Nothing on this pair matched a row in the reference tables behind this check. That is not a clearance: it means these references do not name this combination.
Guideline-based alternatives
That was your demo check, run on the same references the desk uses. The desk adds renal dosing against an estimated clearance, hepatic review, unlimited checks, saved history and your sign-off on every card.
The on-page check covers five prescribing scenarios and never invents clinical output, so it will not produce a card for this pair.
The full Prescriber.io desk checks any regimen against interactions, contraindications, and renal or hepatic dosing, with cited sources for you to verify.
Interaction
Contraindication / allergy check
Dosing guidance (renal / hepatic)
Guideline-based alternatives
Decision support. You verify against official sources and sign.
Clinician in the loopDecision support for licensed clinicians. Prescriber.io does not diagnose or prescribe and is not a substitute for professional clinical judgment.
$24 per clinician a month billed annually. Decision support for licensed US clinicians.
The short answer
Which drug dosage calculator app should a prescriber pay for?
Free calculator apps such as MDCalc and ClinCalc handle the formulas (creatinine clearance, body surface area, ideal body weight) and are worth keeping. What they cannot do is tell you what those numbers mean for a specific drug. Drug references such as epocrates+ ($179.99 a year) and Lexidrug ($29.99 a month) print the adjustments, and you apply them. Prescriber.io joins the two: you describe the patient, name the drug, and it flags the renal, hepatic, weight or age adjustment with the source, for $24 per clinician a month billed annually.
Same patient, two apps
What a calculator returns and what a dosing check returns
Take a 78 year old woman, 52 kg, serum creatinine 1.4 mg/dL, on apixaban for atrial fibrillation, with a urinary tract infection. Type her into a Cockcroft-Gault calculator and you get a creatinine clearance of about 27 mL/min. Correct, and only the start.
The questions that matter come next. Does her apixaban dose still fit, given her age, weight and creatinine? Which antibiotic choices need a lower dose at that clearance, and is nitrofurantoin still a sensible option? A calculator app is silent on all of it, because it never knew which drugs were involved.
A dosing check answers those questions in the same pass, and it shows the threshold that triggered each flag so you can confirm it in the labeling. If renal dosing is most of what you need, the renal dosing calculator page goes deeper, and our creatinine clearance calculator is free to use on its own.
Calculator app
Cockcroft-Gault, actual weight
27
mL/min
Dosing check
Apixaban
Meets 1 of 3 dose reduction criteria (weight 52 kg). Standard dose still applies; recheck if creatinine reaches 1.5.
Nitrofurantoin
CrCl below 30. Labeling and Beers advise against. Alternatives listed.
Cephalexin
Dose and interval adjustment at CrCl 15 to 29. Source cited.
Illustrative example. You verify each flag against current labeling and sign.
Beyond mg per kg
Six things a medication dosing app has to get right
Each one is a place where the arithmetic is easy and the judgment is not.
Kidney function
Most renal adjustments are written against Cockcroft-Gault creatinine clearance, yet the lab reports eGFR. The app has to know which one the labeling used, and which band the patient falls in.
Liver function
Hepatic adjustments are usually tied to Child-Pugh class. A calculator gives you the score; the drug-specific consequence still has to come from somewhere.
Weight and obesity
Actual, ideal or adjusted body weight changes the answer for aminoglycosides, vancomycin, enoxaparin and many others. Picking the wrong weight is the classic silent error.
Pediatric mg/kg with a ceiling
A weight-based dose that climbs past the adult maximum in a heavy teenager is still wrong. The cap matters as much as the mg/kg.
Age and frailty
Older adults need lower starting doses of many drugs, and some belong on the Beers list at any dose. Age belongs in the dose decision, not in a separate lookup.
The rest of the list
A strong CYP3A4 inhibitor already on board can make a normal dose too high. Interactions and dosing are one question, not two.
Weight choice is the one most often skipped. Our guide to dosing software for obese patients covers which drugs use which weight, and the ideal body weight calculator gives you IBW and adjusted weight in one step.
Honest comparison
Drug dosing apps US prescribers use, and what each costs
What each app does for dosing, whether it applies the dose to your patient, and the price each vendor publishes.
| App | What it does for dosing | Applies it to your patient? | Published US price |
|---|---|---|---|
| MDCalc | Formula calculators: creatinine clearance, BSA, ideal and adjusted body weight, scores. | You enter the numbers for each calculator. It does not know which drug you mean. | Free |
| ClinCalc | Web calculators including vancomycin AUC dosing, CrCl and conversions. | One calculator at a time, numbers typed in by you. | Free |
| Medscape | Drug monographs with adult and pediatric dosing, plus a calculator library. | You read the monograph and apply it. | Free, ad supported |
| Epocrates | Drug monographs with dosing, an interaction check and calculators. | You read the monograph and apply it. | Free; epocrates+ $179.99 a year or $24.99 a month |
| UpToDate Lexidrug | Deep monographs with renal and hepatic adjustment fields, pediatric dosing, calculators. | You read the adjustment field and apply it. | $29.99 a month on the app |
| Harriet Lane Handbook app | Pediatric formulary with weight-based doses. | You do the mg/kg math against the listed range. | $54.95 a year, web and app |
| Sanford Guide | Antimicrobial dosing including renal adjustment tables. | You look up the CrCl band and apply it. | $79.99 All Access |
| Clinical Pharmacology (Elsevier) | Monographs plus 300+ calculators, pediatric content incl. Harriet Lane. | You read and apply. | $650 a year, one plan |
| Micromedex | Monographs, dosing tools and NeoFax pediatric content. | You read and apply. | No published price. The app activates only with a hospital login. |
| Prescriber.io | Takes the patient (weight, age, eGFR or CrCl, liver function, other drugs) and flags the dose adjustment for the drug you are about to prescribe, with the reason and source. | Yes. You describe the patient once. | $24 per clinician a month billed annually, $49 monthly |
Prices from each vendor's store page or the US App Store, re-read between September and October 2026. Prices change; check the vendor before you buy.
Where the other apps win
Lexidrug's monographs are deeper than any one-line flag, and if you want to read the full renal and hepatic sections yourself, $29.99 a month buys a lot of reference. Micromedex covers more than anyone in the table and the NeoFax content is the standard for neonatal dosing, but you only get it through a hospital. Harriet Lane is the pediatric formulary residents trust, at $54.95 a year. MDCalc and ClinCalc are free and fast, and nobody should pay for a creatinine clearance formula.
So the honest split looks like this: keep a free calculator, keep one reference you like reading, and add a dosing check if the joining step is where your time or your errors go. Pharmacists comparing the calculator apps side by side will find more in our drug dosing calculator apps for pharmacists guide, and the Epocrates vs Lexicomp comparison covers the two paid references in detail.
How it works
From patient details to a checked dose in four steps
-
1
Describe the patient
Age, weight, height, serum creatinine or eGFR, liver function, allergies and the current medication list. Plain text works.
-
2
Name the drug you are considering
Drug and intended regimen. The check works out which weight and which kidney measure the labeling expects.
-
3
Read the adjustment and the reason
You get the flagged adjustment, the threshold that triggered it and the source, so you can verify it against current labeling.
-
4
Decide and sign
The dose on the prescription is your decision. The app shows its work so you can check it in seconds.
It runs in the browser on a phone, tablet or desktop, so there is nothing to install on a work device. The same check also screens interactions and contraindications, which is why many clinicians use it in place of a separate drug contraindication checker.
Who pays for this
Who buys a drug dosing app instead of using the free ones
Hospital prescribers have pharmacists verifying orders and a licensed drug database inside the EHR. The clinicians who end up paying for a dosing app are the ones working without that net.
Antibiotics are where most outpatient renal adjustments happen, which is why the antibiotic dosing calculator is one of our most used pages, and children get their own pediatric dosing calculator with the adult ceiling built in.
NPs and PAs in outpatient practice
No pharmacist down the hall and a lightweight EHR. Renal adjustments for common antibiotics, anticoagulants and diabetes drugs come up every week.
Physicians who left a hospital system
Micromedex and Lexidrug came with the badge. In private practice the dosing reference has to be paid for per clinician.
Urgent care and telehealth
New patient, a recent creatinine if you are lucky, and a prescription inside ten minutes. Dosing has to be right the first time.
Consultant pharmacists
Medication reviews for long-term care and home health, where kidney function and age drive most of the dose changes.
Prescriber.io
$24
per clinician a month, billed annually. $49 month to month.
Lexidrug app
$29.99
a month. Full monographs with adjustment fields you apply.
epocrates+
$179.99
a year, or $24.99 a month. Basic dosing is in the free app.
Every plan is billed per prescribing clinician. Full detail on the pricing page.
Straight answers
Questions prescribers ask before buying a dosing app
What is the best drug dosage calculator app for doctors?
The best drug dosage calculator app for a prescriber is one that knows the drug and the patient together. Free apps such as MDCalc do the arithmetic well, and Lexidrug or Epocrates list the adjustments, but you still join the two. Prescriber.io takes the patient once and flags the dose adjustment for the drug you name, with the reason.
What app do doctors use to calculate drug dosages?
Most US doctors use a mix: MDCalc or ClinCalc for formulas such as creatinine clearance, and a drug reference such as Epocrates, Medscape, Lexidrug or a hospital Micromedex login for the dose itself. Pediatricians add the Harriet Lane Handbook app. Each app covers one half of the job.
Is there an app that adjusts doses for kidney function?
Yes, in two ways. Reference apps such as Lexidrug and the Sanford Guide print renal adjustment tables you apply yourself. Prescriber.io takes the patient's creatinine or eGFR and flags the adjustment for the specific drug, naming the threshold and source. Free calculators give you the clearance number only.
Is MDCalc free?
Yes. MDCalc is free on the web and in its app, and it is excellent for formulas such as Cockcroft-Gault, ideal body weight and clinical scores. It does not tell you what a creatinine clearance of 28 means for the drug you are about to prescribe; that part comes from a drug reference or a dosing check.
Does Epocrates calculate drug doses?
Epocrates includes medical calculators and drug monographs with adult and pediatric dosing, and the basic app is free. epocrates+ costs $179.99 a year or $24.99 a month. You still read the monograph and apply the adjustment yourself; it does not take a patient profile and return a patient-specific dose.
How much does a drug dosing app cost?
Formula calculators such as MDCalc and ClinCalc are free. Drug references with dosing run from $54.95 a year (Harriet Lane, pediatrics) and $179.99 a year (epocrates+) to $29.99 a month (Lexidrug) and $650 a year (Clinical Pharmacology). Prescriber.io is $24 per clinician a month billed annually.
Can a dosing app replace a pharmacist review?
No. A dosing app catches the adjustment you might miss under time pressure and shows you why. It does not replace clinical judgment or a pharmacist's review of complex regimens. The prescriber verifies the dose against current labeling and signs; the app is decision support.
Related tools
Dosing checks that run alongside this one
Renal dosing calculator
Dose reductions and avoid-below thresholds by kidney function.
ToolDrug dosing calculator
Weight, renal and hepatic adjustments with cited sources.
CalculatorVancomycin calculator
AUC-guided dosing for one of the hardest drugs to dose.
ReferenceHepatic impairment drug dosing
Child-Pugh based adjustments by drug class.
Buyer's guideBest drug reference app
The paid references compared on depth and price.
PricingLexidrug subscription cost
What the $29.99 a month app includes.
Get the dose adjustment before the prescription goes out
Renal, hepatic, weight and age adjustments, interactions and contraindications in one check, with a cited reason on every flag. You review, verify, and sign.
Decision-support for licensed clinicians. Prescriber.io does not diagnose or prescribe autonomously and is not a substitute for professional clinical judgment. MDCalc, ClinCalc, Medscape, Epocrates, UpToDate, Lexidrug, Harriet Lane, Sanford Guide, Clinical Pharmacology and Micromedex are trademarks of their owners. Prescriber.io is not affiliated with any of them.