How Long Does it Take For Antibiotics to Work?

By Zina Semenovskaya, MD
Medically reviewed
October 25, 2021

If you’ve ever suffered from a urinary tract infection (UTI), pneumonia, or another bacterial infection, you know how antibiotics can bring you back to health.

Still, not all conditions treated with antibiotics improve at the same speed.

When you’re in pain, it can sometimes feel like the antibiotic prescribed is taking longer than expected to clear the infection.  

In this article, I’ll describe the different types of antibiotics and what they’re used to treat.

I’ll also cover how long most antibiotics take to work, and where you can get a prescription filled.

Finally, I’ll explain when you may want to reach out to a doctor for help. 

Do you have further questions about antibiotics? Chat with a doctor today for just $23.

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What Are Antibiotics Used For?

Antibiotics are used to cure bacterial infections.

They work by destroying bacteria and preventing their reproduction.

Antibiotics should only be used to treat certain bacterial infections, and they are not at all effective against viral infections. 

Your doctor can prescribe oral, topical, or intravenous antibiotics for a diverse range of bacterial infections, including:

In some cases, antibiotics can be life-saving, especially if you’ve been diagnosed with a serious illness like bacterial meningitis or sepsis, or if you’re at a higher risk of bacterial infection, including if you’re immunocompromised or receiving chemotherapy.

What Are Some Common Antibiotics?

Antibiotics are often classified into groups.

Here are some of the most common groups of antibiotics:

  • Penicillins and penicillin-based: These are among the oldest antibiotics, and are a first-line treatment for many conditions, including UTIs and respiratory tract infections. Amoxicillin is an example of a penicillin class antibiotic.
  • Tetracyclines: Often prescribed for common conditions like acne, skin infections, tick-borne illnesses, respiratory infections, and more.
  • Cephalosporins: These antibiotics treat a wide range of infections, including ear infections, pneumonia, and meningitis.
  • Macrolides: A common alternative for people who are allergic to penicillin, these antibiotics are used to treat some types of pneumonia, STDs, and other infections. Clindamycin and azithromycin are examples of macrolide antibiotics.
  • Fluoroquinolones: These versatile antibiotics, including ciprofloxacin and levofloxacin, are used to treat a variety of skin, sinus, joint, and urinary infections. However, fluoroquinolones can interact with many common medications and may have some serious side effects.
  • Sulfonamides: The most commonly prescribed sulfonamide is trimethoprim-sulfamethoxazole, sold under the name Bactrim or Septra. Sulfonamides work by stopping or slowing the growth of bacteria, and are often used for UTIs and skin infections.

How Long Do Antibiotics Take to Work?

The length of time it takes for an antibiotic to clear an infection depends on many factors, including the condition being treated and which antibiotic you’ve been prescribed.

Although antibiotics start working as soon as you take them, it can take several days for you to begin feeling the effects.

Unfortunately, the optimal length of antibiotic treatment is still understudied and as a result, not standardized.

Until recently, longer courses of antibiotics were thought to help prevent antibiotic resistance, but a newer study suggests that the opposite may be true.

According to the study, shorter antibiotic treatments of certain conditions may be just as effective at clearing an infection and potentially more effective at preventing resistant bacteria from developing.

In fact, this was particularly true for treatment of strep throat (which accounts for approximately one-third of all sore throats in children), cellulitis, and pneumonia. 

If you feel like your antibiotics aren’t working, don’t stop taking them.

It’s important to finish the entire course of antibiotics that have been prescribed by your doctor or pharmacist.

If you’re concerned that you’re not getting better, talk to your provider.

How Do You Get Antibiotics?

In the United States, oral antibiotics are only available via prescription, so you need to speak to a medical professional to obtain them.

The provider will ask about your symptoms and medical history, and may run additional tests to determine which antibiotic medicine, if any, is right for you.

Online pharmacies are also a safe and convenient way to buy prescription medication.

Keep in mind that you’ll still need to talk to a licensed healthcare provider first to get a prescription for the correct antibiotic—but that doesn’t mean you need to speak with them in person.

You can speak with a provider online through many available and secure telehealth platforms, including the K Health app, to discuss your symptoms and get a prescription for antibiotic medication if appropriate.

Once you have a prescription, you can order antibiotics from licensed online pharmacies or directly through some telehealth platforms.

Do you have further questions about antibiotics? Chat with a doctor today for just $23.

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When to See a Doctor

If you think you may have signs or symptoms of a bacterial infection, the best way to get information is to talk to your provider.

They can help determine whether an antibiotic prescription is right for you, and how long it will take to clear the infection.

The sooner you receive the appropriate treatment, the sooner you can start feeling better.

How K Health Can Help 

Did you know you can get affordable primary care with the K Health app?

Download K to check your symptoms, explore conditions and treatments, and if needed text with a doctor in minutes. K Health’s AI-powered app is HIPAA compliant and based on 20 years of clinical data.

Frequently Asked Questions

How can you tell if antibiotics are working?
Unfortunately, there’s no way to tell if antibiotics are working. Though antibiotics start working as soon as you take them, it can take several days for you to begin feeling the effects. However, by the end of your recommended course, you should feel a noticeable difference in (or total disappearance of) your symptoms.
What is antibiotic resistance?
Antibiotic resistance occurs when bacteria have found a way to survive the medication designed to kill it—not when your body has become resistant to antibiotics. Antibiotic resistance is a growing issue both nationally and internationally, with some bacteria exhibiting resilience to the most powerful antibiotics available.
Can you make antibiotics work faster?
Unfortunately, there is no way to make antibiotics work faster. Regardless of your condition or the antibiotic being used, always follow the instructions as provided by your doctor or pharmacist.
K Health articles are all written and reviewed by MDs, PhDs, NPs, or PharmDs and are for informational purposes only. This information does not constitute and should not be relied on for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.

Zina Semenovskaya, MD

Dr. Semenovskaya specializes in emergency medicine, and received her medical degree from Weill Cornell Medical College. She is currently the medical director at Remote Emergency Medicine Consulting, LLC and splits her time working clinically as an emergency medicine attending in California and Alaska. She is the first of our doctors to be fluent in Russian.