Azithromycin
Dose Calculator

To calculate a child's azithromycin dose, multiply the weight in kg by the prescribed mg/kg, usually 10 mg/kg on day 1 and 5 mg/kg on days 2 to 5. Cap it at 500 mg on day 1 and 250 mg after that. Then divide the mg by the bottle's mg per mL to get the volume.

An Azithromycin pediatric dose calculator turns a child's weight into a measurable liquid dose. It matches that weight to the prescribed plan. Then it shows exactly how much medicine goes into the syringe each day. The goal is simple: the right mL on every day of the course.

Most parents search for an azithromycin dose by weight for child use, and that is exactly how this antibiotic is dosed. Azithromycin, sold under the brand name Zithromax, is prescribed in mg/kg. That means the child's weight drives every number on the screen. To start, enter weight in kilograms from a recent weigh-in. A rough guess can throw off each dose by several percent.

Next, choose the Zithromax schedule your prescriber wrote. What is the Zithromax pediatric dosing schedule? The official Zithromax label sets the plan by infection. Ear infections allow a single 30 mg/kg dose, a 3-day plan, or a 5-day plan, and pneumonia uses the 5-day plan. Strep throat takes 12 mg/kg once daily for five days. Pick the wrong dosing schedule, and every later number goes wrong with it.

The 5-day plan is the one parents meet most often. What is the azithromycin day 1 dose? It is 10 mg/kg, with no more than 500 mg on that first day. What is the azithromycin follow-up dose? It drops to 5 mg/kg once daily on days 2 to 5, up to 250 mg a day. That larger day-1 dose front-loads the course, and each follow-up dose keeps it going.

Then choose the suspension strength. Which Zithromax suspension strength to use? The pharmacy label decides, not habit or memory. The oral suspension is made in two strengths, 100 mg per 5 mL and 200 mg per 5 mL. The stronger bottle halves the mL for the same milligrams, which is exactly where mix-ups happen.

How to convert azithromycin mg/kg to mL? Multiply the weight by the mg/kg dose, then divide by the bottle's mg per mL. This tool does both steps at once, so it can convert the day-1 and follow-up mg/kg doses together. Here is how to calculate azithromycin dose for a child weighing 12 kg on the 5-day plan:

Every pediatric dose still needs clinician confirmation before the first spoonful. A clinician checks the infection, the plan and any allergy history. When I test calculators, the ones I trust show the mg and the mL side by side. That lets a pharmacist check both in seconds. Treat the azithromycin pediatric dose calculator by weight as your second pair of eyes, never as the prescription itself.

Enter the patient's weight (in kg, g, or lb), age (years and months), and select a dosing regimen. Each preset encodes the full dosing schedule — Day 1 loading dose and Days 2–5 maintenance doses — aligned with the clinical indication.

The calculator returns the per-dose amount in mg, the volume of suspension (for liquid formulations), and a day-by-day dosing schedule summarising each dose and its maximum. Results are displayed with inline warnings for relevant safety concerns.

QT prolongation warning is prominently displayed for all calculations, with a persistent alert reminding clinicians to screen for QT risk factors before prescribing.

Age warnings alert when patients are under 6 months — azithromycin is approved for paediatric use from 6 months for most indications, and its use in younger infants requires specialist guidance and has been associated with pyloric stenosis in neonates.

Volume results can be rounded to the nearest 0.5 mL increment to align with standard oral syringe graduations, reducing practical measurement errors.

This Azithromycin calculator works as a fast parent page for three jobs. It runs weight-based dose checks, handles the mL conversion and lists the common strengths. It also adds the practical safety steps that generic calculator sites often skip. Treat its answer as a check on the prescription, never a replacement for it.

Azithromycin dosing rarely goes wrong because of hard math. It goes wrong at the edges: the wrong bottle, the wrong schedule, or a guessed weight. These azithromycin pediatric dose calculator details target exactly those weak spots. A good azithromycin calculator for parents should answer how to check azithromycin dose by weight, how to convert azithromycin to mL, and what are common azithromycin strengths. Which azithromycin safety steps do calculators skip? Mostly the strength check and the schedule check, both covered below.

Practical azithromycin dosing comes down to matching three things before the first dose. You need the right course length, the right amount for each day, and the right bottle. Most home mistakes happen when one day's amount is used on another day or when the wrong strength is read.

Before you measure the dose, line up the whole course on paper. Write down the day-1 loading dose, then the later-day doses. Check the suspension strength in hand against the label, not your memory. This short azithromycin dose setup takes two minutes before starting the course.

What to check before measuring azithromycin? The days, the doses and the bottle. What is an azithromycin loading dose? It is a bigger first dose that builds drug levels quickly, so smaller doses can keep them steady. Which suspension strength do I have? Read the mg and mL numbers printed on the label of the suspension.

The Formula Behind Each mL: The Azithromycin dose formula needs only three moves. Multiply the child weight in kg by the prescribed mg/kg/day. Then divide by the doses per day to get each dose in mg. Finally, divide by the medication concentration, written as mg per mL, to get the mL per dose. In short:

How to calculate mL per dose without mistakes? Work in mg first and switch to mL last. The daily dose in mg stays the same whichever bottle you hold, so it is your anchor. That is the azithromycin dose formula for children in practice. How to divide a daily dose? Azithromycin is usually given once a day, so the daily amount is the single dose. How to use medication concentration in mg per mL? Convert the label first: 200 mg per 5 mL equals 40 mg per mL. No formula can fix a guessed weight, so weigh the child on a scale.

This azithromycin work example takes under a minute. A 20 kg child is prescribed 10 mg/kg/day, given 1 time daily, using 200 mg/5 mL. First, find the daily mg target: 20 × 10 = 200 mg. Then divide by the schedule; once a day means one 200 mg dose. Finally, convert that mg amount into mL for the selected product: 200 ÷ 40 = 5 mL. So, how many mL of azithromycin 200 mg/5 mL for 20 kg? Five mL on this plan, and that is the full azithromycin dose for a 20 kg child each day.

Here is an alternate example that shows the cap at work. A 55 kg teenager on the same 10 mg/kg/day plan calculates to 550 mg. The Zithromax label caps this plan at 500 mg a day, so the dose stops there. With the 200 mg/5 mL bottle, that capped dose is 12.5 mL. A tool showing 13.75 mL has ignored the ceiling, and that is a red flag for the whole calculator.

Common calculator choices include 10, 12 or 30 mg/kg/day, or other mg/kg targets depending on the prescription. Which mg/kg dose is right for azithromycin? The one your prescriber chose, because each one fits a different infection. Here is the 20 kg child across all three plans:

Use this table as a reality check, not a menu. Confirm the prescription's dose basis before trusting any mL result. Is the number per day, per dose, or for the whole course? In my calculator reviews, that one question explains most of the wrong answers I find.

Strength conversion is where most mix-ups hide. The two liquid strengths are 200 mg/5 mL and 100 mg/5 mL. The same mg target creates a different mL dose when the bottle or tablet strength changes. Why does the mL change with strength? A stronger liquid packs more drug into each mL, so you need less of it. For any other product, our mg to mL calculator runs the same conversion in seconds.

Schedule and course come last. Is azithromycin given once daily? Yes, and the available schedules here are once a day, with course options shown in the calculator. How long is an azithromycin course? The Zithromax label sets one, three or five days for children, depending on the infection. Match the frequency and duration to the clinician's plan rather than picking the easiest volume to measure.

Community-acquired pneumonia (5-day course): Day 1: 10 mg/kg (max 500 mg) as a loading dose; Days 2–5: 5 mg/kg/day (max 250 mg). This regimen achieves therapeutic tissue concentrations for atypical and typical respiratory pathogens and is the most common outpatient course.

Pharyngitis / tonsilitis (5-day course, penicillin allergy): 12 mg/kg/day (max 500 mg) for 5 days as a once-daily dose. This regimen delivers higher tissue levels appropriate for Streptococcus pyogenes eradication.

Pertussis treatment and post-exposure prophylaxis: 10 mg/kg (max 500 mg) on Day 1; 5 mg/kg/day (max 250 mg) on Days 2–5. The 5-day course is standard for both treatment and prophylaxis in contacts.

Single-dose chlamydia treatment (adult/adolescent): 1 g as a single dose — this regimen is not weight-based and is used in patients ≥ 15 years or ≥ 45 kg who can take adult doses.

How does a 5-day azithromycin course work? Many pediatric azithromycin plans start with a higher day-1 dose. Lower once-daily doses then follow on the remaining days. Why is the day-1 azithromycin dose higher? The bigger first dose fills the tank, so later doses only top it up.

The key mistake is mixing the two amounts. Using the later-day amount on day 1, or vice versa, throws off the whole 5-day course. What if I give the day-1 dose on day 2? Call the pharmacist before the next dose rather than guessing a fix. Here is a day-by-day example for a 16 kg child on the common 10-then-5 mg/kg plan:

Some indications use the same once-daily dose for 3 days instead of a 5-day tapering-style course. When is a 3-day azithromycin course used? The Zithromax label lists it for children with ear infections and sinus infections, at 10 mg/kg once daily. For the same 16 kg child, the 3-day course means 160 mg, or 4 mL of the stronger bottle, on each of the three days.

Is a 3-day azithromycin course the same as a Z-Pak? No. The familiar adult Z-Pak pattern is a 5-day pack: 500 mg on day 1, then 250 mg daily. So follow the prescribed regimen instead of assuming. 3-day vs 5-day azithromycin for ear infections? Both deliver the same total of 30 mg/kg, just spread differently.

These alternative dosing regimens follow the condition, not just the age. Dosing regimens by condition are where online charts most often go wrong, so this version follows the label:

What is the azithromycin dose for pneumonia in children? From 6+ months, it is the 5-day plan in the chart above. What is the azithromycin dose for an ear infection? There are three label options: one 30 mg/kg dose, 10 mg/kg daily for 3 days, or the 5-day plan. Can azithromycin be taken with food? Yes, the liquid works with or without food.

Some charts list sinusitis as adults only, with extended-release available. In fact, the pediatric label includes sinusitis in children at 10 mg/kg for three days. Other charts mark skin infections for all ages, but the pediatric label does not list them, so the doctor sets that dose.

Two age restrictions matter most. Can babies under 6 months take azithromycin? For pneumonia and ear infections, safety and effectiveness not established at that age, so doctors decide case by case. Whooping cough is the exception, since the CDC prefers azithromycin even for newborns. Can a 1 year old take azithromycin for strep throat? It is not recommended under 2 years for pharyngitis or tonsillitis. For children in these age groups, always consult your pediatrician before using any chart.

Adult azithromycin doses follow the infection, not the body weight. Most adult courses use 500 mg on the first day and 250 mg on the next four days, or 500 mg a day for three days. Once a teen's weight-based dose reaches these amounts, the adult dose becomes the ceiling, which is exactly where this calculator stops the dose.

Day 1 loading dose (10 mg/kg, max 500 mg) and Days 2–5 maintenance dose (5 mg/kg, max 250 mg). Volume calculated for 200 mg/5 mL suspension.

What is the azithromycin dose by age? Age gives only a rough range, because weight decides the real number. Getting the correct azithromycin dosage is crucial for effective treatment, so these age-specific dosage guidelines start from your child's age and weight together. What is the azithromycin dose by weight? Most plans use 10 mg per kg on the first day, then 5 mg per kg. The charts below give comprehensive dosing information, checked against the Zithromax label.

This pediatric dosage chart uses the common 5-day ear-and-chest plan as its standard dose: 10mg/kg once daily on Day 1, then 5 mg/kg on days 2 to 5. Each age group and weight range has its own example child, with the mL shown for the 200 mg/5 mL bottle. With the 100 mg/5 mL bottle, simply double every mL figure.

A few special notes change the dose or the duration. For babies, weight-based dosing required means no shortcuts by age. What is the azithromycin dose for a 1 year old? Usually 10mg/kg on the first day, which is about 100 mg for a 10 kg child. Some charts list 10-12mg/kg for this age, but the higher 12mg/kg plan is for strep throat and is not for pharyngitis/tonsillitis under 2 years.

What is the azithromycin dose for a 5 year old? On the strep throat plan, which can treat pharyngitis/tonsillitis from age 2, it is 12mg/kg once a day for 5 days. A 14 kg child would get 168 mg a day, or 4.2 mL of the 200 mg/5 mL bottle. Other plans run for 3-5 days, depending on the infection.

When do kids switch to adult azithromycin dosing? Not automatically at 12+ years or 34+ kg, as some charts suggest. Weight-based doses continue until they reach the adult caps, which happens at about 50 kg.

Every 5-day azithromycin course for an ear or chest infection adds up to 30 mg/kg in total: 10 mg/kg on day 1, then 5 mg/kg on each of the next four days. The 1-day and 3-day ear-infection plans reach the same 30 mg/kg total. That single number tells you whether the bottle in your hand will last.

Zithromax suspension comes in four bottle sizes once mixed: a 300 mg bottle of the 100 mg/5 mL strength, and 600 mg, 900 mg and 1,200 mg bottles of the 200 mg/5 mL strength. On a 30 mg/kg course, each bottle covers a child up to a set weight:

At those exact weights, the course uses the whole bottle on paper, with nothing spare for a spill or a dose that is spat out. A 20 kg child on the 5-day plan needs 600 mg, or exactly 15 mL. The strep throat plan needs twice as much: 12 mg/kg for five days adds up to 60 mg/kg, so the same child needs 1,200 mg, or 30 mL. If the bottle looks too small for the plan, ask the pharmacist before day 1, not on day 4.

Timing and Food: Azithromycin timing and food rules depend on the form. Should azithromycin be taken with food? Tablets and the liquid can be taken with or without food. Give them at the same time each day for consistency.

Capsules are different: When should azithromycin capsules be taken? At least 1 hour before meals or 2 hours after eating. Does food affect azithromycin absorption? For capsules, yes, and this spacing ensures proper absorption. These timing and food considerations are worth checking on the pharmacy label before the first dose.

Shake the bottle well before each use. Reconstituted suspension should be stored at room temperature or refrigerated and used within 10 days.

The long tissue half-life of azithromycin means that a 5-day course provides tissue concentrations that persist for up to 10 days after the last dose — which is why shorter courses can be as effective as longer courses of other antibiotics for the same indications.

Choose the exact suspension strength or tablet plan before calculating mL. That keeps the day-1 and later-day doses accurate from start to finish. Azithromycin forms and strengths each suit a different child:

Which azithromycin suspension strength is best for my child? Small children on low doses often do well with the weaker bottle, while bigger children usually suit the stronger one. Can children take azithromycin tablets? Yes, once they can swallow them safely and the tablet strength fits the plan.

Always confirm which day of the course you are on before using the suspension table. Why does the azithromycin mL change after day 1? On a 5-day plan, the measured mL may change after the loading dose. Tick off each day on the box so nobody loses track.

Azithromycin blocks the hERG potassium channel, which delays ventricular repolarisation and prolongs the QT interval on the ECG. In susceptible individuals, this can precipitate Torsade de Pointes — a potentially fatal ventricular arrhythmia.

Risk factors for azithromycin-related cardiac events include: female sex, pre-existing prolonged QT, hypokalaemia, hypomagnesaemia, bradycardia, congenital long QT syndrome, and concurrent use of other QT-prolonging drugs (e.g., antipsychotics, fluoroquinolones, ondansetron, some antifungals).

Regulatory agencies have issued warnings about azithromycin's cardiac risk. In 2013, the FDA updated labelling to include information about QT prolongation and fatal arrhythmias. For most healthy children at standard doses, the absolute risk is low — but screening for risk factors is mandatory before prescribing.

Regulatory agencies have issued warnings about azithromycin's cardiac risk. In 2013, the FDA updated labeling to include information about QT prolongation and fatal arrhythmias. For most healthy children at standard doses, the absolute risk is low — but screening for risk factors is mandatory before prescribing.

QT-risk context matters more when a child has dehydration, a known heart-rhythm risk, or takes other QT-prolonging medicines. Which medicines interact with azithromycin QT? Certain heart-rhythm drugs are the main concern, so ask your pharmacist to check the full list.

Azithromycin is a macrolide antibiotic with activity against a broad range of gram-positive and atypical organisms (Mycoplasma, Chlamydophila, Legionella). Its uniquely long tissue half-life (2–4 days) and intracellular accumulation allow for short, convenient dosing regimens — most commonly a 5-day course for respiratory infections.

In pediatrics, azithromycin is used as a second-line or alternative first-line antibiotic for community-acquired pneumonia (particularly atypical), pharyngitis (in penicillin-allergic patients), pertussis prophylaxis and treatment, otitis media (in penicillin allergy), and chlamydial infections.

The drug's Z-pack reputation for convenience has made it one of the most commonly prescribed antibiotics worldwide — but it is also associated with significant antimicrobial stewardship concerns due to overuse, increasing macrolide resistance among respiratory pathogens, and its cardiac side effect profile.

Azithromycin safety checks start with the bottle. Use the exact product strength in hand before measuring the dose, and before using the result at all. Then confirm the maximum dose, age limits and any indication-specific cautions. What is the maximum azithromycin dose for a child? Pfizer's label caps it at 500 mg on the first day and 250 mg on each later day of a 5-day course. A single 30 mg/kg dose must not exceed 1,500 mg.

Is azithromycin safe for all ages? Not automatically. Age limits differ by infection, so the prescriber checks them before choosing a plan. These safety checks matter most for babies and toddlers, whose doses are smallest and easiest to get wrong.

Escalate urgent symptoms or medication reactions instead of repeating doses from calculator output alone. What to do if a child reacts to azithromycin? Stop and call the prescriber, and call emergency services for swelling or breathing trouble. Reactions are not rare. CDC researchers estimated about 70,000 US emergency visits a year by children for antibiotic side effects, and most were allergic reactions such as rash or swelling. Can you repeat an azithromycin dose? Only when the prescriber says so.

Double-check before dosing, on every day of the course. This pre-dose double-check starts with one match: the day-1 dose against the later once-daily doses. Get that right before measuring the liquid.

If severe vomiting, fainting or palpitations occur, reassess the plan instead of simply continuing. What if my child faints on azithromycin? Seek urgent care, since fainting can signal a rhythm problem. Should I give the next azithromycin dose after vomiting? Not before calling the prescriber, who decides about the next dose.

Want to know what azithromycin treats, how to give it at home and which side effects to watch? Read our complete guide to azithromycin for children.

Medical disclaimer: This page is for educational purposes only and is not medical advice. BestMedCal's tools check arithmetic and explain methods; they do not prescribe. Always confirm the dose, schedule and maximum with your child's prescriber or pharmacist.