How Long Does it Take for Azithromycin to Work? - GoodRx (2024)

Key takeaways:

  • Azithromycin (Zithromax), commonly called a “Z-Pak,” is a popular antibiotic. It starts to make a difference after a few days of taking it.

  • You can take azithromycin with or without food. But if you experience an upset stomach or diarrhea while taking azithromycin, taking your next dose(s) with food may help control your symptoms.

  • Azithromycin is available as a lower-cost generic medication. GoodRx can help you save over 86% off the average retail price at certain pharmacies.

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Azithromycin (Zithromax), commonly referred to as a “Z-Pak,” is an antibiotic that treats a variety of mild to moderate infections. You may have received it for bacterial infections ranging from strep throat and pneumonia to conditions like chlamydia.

Azithromycin is also a well-tolerated antibiotic that’s been around for decades. It’s pretty affordable, too. But that doesn’t mean it’s always straightforward to use.

What is azithromycin?

Azithromycin is a prescription-only antibiotic. It’s available as a pill and liquid that’s usually taken by mouth for 1 to 5 days. It’s also available as an infusion given into a vein. The best dosage and formulation of azithromycin depends on your medical history and how serious your infection is.

A type of macrolide antibiotic, azithromycin works primarily by preventing the growth of bacteria. It helps your immune system get rid of the infection that’s causing your symptoms.

5 pharmacist-backed tips for taking azithromycin

Azithromycin is generally an effective antibiotic for adults and children aged 6 months and older. However, azithromycin’s effects can be slightly different for everyone. Below are the top five pharmacist tips for taking azithromycin.

1. How long does it take azithromycin to work?

Azithromycin starts working soon after you take your first dose. Oral azithromycin usually needs about 2 to 3 hours to reach its full concentration in your body, but the effects might not be noticeable right away.

You should start to feel better after a few days of taking azithromycin. However, the specific number of days varies for everyone. How fast it works — and how long you need to take the medication — depends on your infection.

As with all antibiotics, it’s important to take all of your prescribed azithromycin doses. This is true even if you feel better before all of your doses are finished.

2. Should I take azithromycin with food?

You can take azithromycin with or without food. Food doesn’t change its effectiveness. But if you experience side effects like upset stomach or diarrhea after taking a dose, taking azithromycin with food with the next dose may help.

If you continue to experience symptoms of an upset stomach, reach out to your healthcare provider. They can help offer tips on how to get your symptoms under control. You could also ask them about possibly trying a probiotic supplement to lessen your stomach-related side effects. Probiotics may help prevent diarrhea associated with antibiotics like azithromycin.

3. Should I separate azithromycin from any medications?

Yes, some medications can interact with azithromycin. They can affect its absorption, potentially making it less effective.

If you plan on taking an aluminum- or magnesium-containing antacid while you’re taking azithromycin, ask your pharmacist how long you should space them apart. If they’re in your stomach at the same time, they could make azithromycin less effective. This could lead to an undertreated infection.

Other interactions are also possible, but they have less to do with the timing of your doses. One key interaction is with certain heart rhythm medications (antiarrhythmics). Top examples are amiodarone (Pacerone), quinidine, and sotalol (Betapace). It’s not intentional, but azithromycin can have an effect on your heart rhythm. When azithromycin is combined with heart rhythm medications like these, there’s a greater chance of experiencing QT prolongation — a type of dangerous, irregular heartbeat.

Azithromycin interactions are discussed more in a previous GoodRx Health article.

4. What happens if I miss my dose of azithromycin?

If you miss a dose, take it as soon as you remember. But if it's close to the time of your next scheduled dose, skip the missed dose altogether. At that point, plan to take your next dose as scheduled, and don’t double up on doses.

Taking your antibiotic as consistently as possible helps maximize its effectiveness. But we’re all human — it’s natural to forget a dose every now and then. To help with this, try to think about ways to remember your scheduled doses that fit your lifestyle. You can try setting an alarm to take it at breakfast. Or if you use a smartphone, you could consider downloading a free medication reminder app.

5. What can I do if I experience side effects from azithromycin?

As with all medications, azithromycin has possible side effects. Some side effects are mild and manageable, while others are more serious and rare.

Certain side effects are also more likely to happen in certain situations. For instance, stomach-related side effects are more common when you take high azithromycin doses over a short period of time. The good news is that most side effects tend to go away once you stop taking azithromycin.


Diarrhea is the most common side effect of azithromycin. It can be a drag, but there are things you can do to try to minimize this symptom.

Diet changes are one option. And in addition to taking your doses with food, try eating foods high in potassium — like bananas, potatoes, and spinach. Drinking plenty of fluids and steering clear of greasy, spicy, or high-fiber foods can also help. When needed, over-the-counter (OTC) antidiarrheals, like loperamide (Imodium A-D), are also an option.

Nausea and vomiting

Nausea and vomiting are also possible with azithromycin. Similar to diarrhea symptoms, making small changes to your diet can make a difference. Try eating more slowly, consuming smaller meals, and avoiding food with strong smells. Nausea medications may also help.

Stomach pain

Another common azithromycin side effect is mild to moderate stomach pain. This pain is usually temporary, but it can sometimes turn serious.

Very rarely, severe stomach pain is possible. It may be related to liver damage or a possible Clostridium difficile (“C diff”) infection. This type of infection can be caused by antibiotics, including azithromycin. If you experience a fever and cramps alongside watery diarrhea and severe stomach pain, this could be a sign of a “C diff” infection. You should seek medical attention right away if so.

Serious side effects

In addition to Clostridium difficile infections, other rare but serious side effects are also possible.

Azithromycin has the potential to cause abnormal heart rhythms. In 2013, the FDA released a warning that stated azithromycin can change your heart’s electrical activity. This may lead to potentially fatal heart rhythms. People at higher risk for this include those with QT prolongation, low levels of potassium or magnesium, or a slower-than-normal heart rhythm. Contact your healthcare provider if you notice any changes in your heart rhythm.

Severe skin reactions have also been reported, including medical emergencies like Stevens-Johnson syndrome, toxic epidermal necrolysis, and drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome. If you see signs of painful blisters or rashes while taking azithromycin, stop taking the medication and seek medical help right away.

Allergic reactions are also possible, albeit rare. If you experience trouble breathing or swelling of the lips, face, or tongue at any point, call 911 or go to the closest emergency care center.

Tips on how to save money with your azithromycin prescription

There are many ways to save on Zithromax and azithromycin. Zithromax is available as a brand-name medication, but you can also find azithromycin as a lower-cost generic.

GoodRx can help you save over 86% off the average retail price of the generic version of azithromycin. Generic azithromycin at certain pharmacies is less than $5 with a free GoodRx discount.

The bottom line

Azithromycin is a prescription antibiotic. In most cases, it helps reduce infection-related symptoms in just a few days. It’s well-tolerated overall, and you can take it with or without food. But if you experience stomach-related side effects, consider taking it with food to help lessen your symptoms. If you have any questions about azithromycin, reach out to your healthcare provider or pharmacist.


MedlinePlus. (2022). Azithromycin.

National Center for Complementary and Integrative Health. (2019). Probiotics: What you need to know.

View All References (3)


Patel, P. H., et al. (2022). Macrolides. StatPearls.

Proficient Rx. (2022). Azithromycin [package insert].

U.S. Food & Drug Administration. (2018). FDA drug safety communication: Azithromycin (Zithromax or Zmax) and the risk of potentially fatal heart rhythms.

GoodRx Health has strict sourcing policies and relies on primary sources such as medical organizations, governmental agencies, academic institutions, and peer-reviewed scientific journals. Learn more about how we ensure our content is accurate, thorough, and unbiased by reading our editorial guidelines.

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How Long Does it Take for Azithromycin to Work? - GoodRx (2024)
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