How Long Does It Take for Antibiotics to Work?

Anyone who has ever had a bacterial infection, such as an ear infection or UTI, knows how effective antibiotics can be when you are sick at making you feel better.

However, sometimes it may feel like the antibiotic is taking too long to start working, which can make you wonder if it is working at all.

Let’s discuss how long antibiotics take to work, what they do, and what happens if you stop taking an antibiotic because you think it isn’t working.

Table of Contents

What Are Antibiotics?

Antibiotics are a type of medication used to treat bacterial infections.

They are a very common type of medicine, yet they are also extremely powerful against bacteria.

Antibiotics are typically classified into different groups, such as:

  • Penicillins
  • Cephalosporins
  • Tetracyclines
  • Fluoroquinolones
  • Macrolides
  • Sulfonamides
  • glycopeptides

These classes are grouped based on similarities between the antibiotics’ chemical structures. However, the individual antibiotics within each class still affect the body differently and may be effective against different bacteria.

Antibiotics are often considered as first-line or second-line treatment. First-line treatments, such as most penicillins, are often the first antibiotics prescribed for an infection because they are statistically effective while having limited side effects. Typically, first-line antibiotics are part of a standard set of treatments. 

First-line treatments may also be effective against a range of bacteria, increasing the odds of being successful in treating the infection.

However, if a first-line antibiotic is not effective, a second-line treatment may be used to clear the infection. These antibiotics can be more effective, but in many cases, they are more expensive than first-line antibiotics.

How Do Antibiotics Work?

There are two primary mechanisms by which antibiotics work.

The first mechanism involves directly killing the bacteria, which is usually accomplished by interfering with the cell contents or the bacterial cell wall formation.

The second mechanism consists of impacting how the bacteria grows and reproduces. Some antibiotics are able to inhibit the bacteria from making specific proteins or releasing certain chemicals, which then stops the bacteria from growing and spreading.

How Long Do Antibiotics Take to Work?

Antibiotics start to work as soon as you take them.

However, you will not notice an improvement in symptoms immediately, as it takes some time for the antibiotic to begin destroying the bacteria or affecting their growth. How long this takes to happen will depend on various factors, such as the antibiotic prescribed and the condition it is treating. In many cases, antibiotics are prescribed for 7 to 14 days, and the antibiotic continues working after the last dose as it is cleared from your system

Unfortunately, there is no way to know when you will start to feel better, although, by the end of the antibiotic course, you should notice an improvement in your symptoms.

If you have been taking your antibiotics for a few days and notice no improvement in symptoms, bring it up with your doctor. They may have you wait a few more days, or they may decide to switch you to another antibiotic.

What Are Antibiotics Used to Treat?

Antibiotics are used to treat infections due to bacteria.

With hundreds of antibiotics that can be prescribed, there’s a wide range of infections that they can treat, including:

However, each antibiotic works in its own way, meaning it can often treat only one infection or a group of infections.

For example, nitrofurantoin is an antibiotic that is typically used only for UTIs because it is only effective in the urine. Because of this, it would not be effective in treating infections in the lungs, brain, or anywhere that urine does not pass.

It is important to note that antibiotics are only effective against illnesses that are due to bacterial infections, not any infection. This means that antibiotics will not help with a cold or flu since these illnesses are due to a virus, not bacteria.

Taking antibiotics when it is not necessary, such as when the illness is due to a virus, can increase the risk of antibiotic resistance.

What Happens If You Go Off Antibiotics Early?

In some cases, you may feel as though your antibiotic isn’t helping with your infection, so you decide to stop taking it. However, even though you still had some symptoms, it’s possible that the antibiotic was still helping to clear the infection, it just needed more time.

If you ever feel as though your antibiotic is not working, it is best to discuss this with a doctor instead of discontinuing the antibiotic on your own.

In other cases, someone may notice that their symptoms have gone away and decide to discontinue their antibiotic treatment before the entire course has been taken. However, doing this can cause riskier and more severe conditions.

The first risk is that the antibiotic did not entirely clear the infection. Most of the infection may have been treated, which is why symptoms can get better, but if antibiotics are discontinued early, some bacteria may still be lingering. This then increases the risk of another infection.

Discontinuing your antibiotics early also increases the risk of antibiotic-resistant bacteria, which are much more challenging to treat and may cause more severe illnesses.

What Is Antibiotic Resistance?

Antibiotic resistance is a growing concern as antibiotics are being overprescribed or used incorrectly. It refers to the bacteria (not your body) being resistant to antibiotics.

Antibiotic-resistant bacteria are not affected by antibiotics and have found a way to survive the medication. This then makes treating infections much more difficult, as different types of antibiotics are needed to try and fight these bacteria.

Antibiotic-resistant bacteria are also dangerous because someone may think that they treated the infection with antibiotics when in reality, the bacteria are still there and may now spread to other areas and cause further harm. 

What Are the Common Side Effects of Antibiotics?

Some of the most common side effects of antibiotics include:

  • stomach upset
  • nausea
  • vomiting
  • diarrhea
  • rash

For those experiencing an upset stomach due to antibiotics, there are some actions you can take to help, including consuming prebiotic-rich foods and taking your antibiotics with food.

Some less common side effects include:

  • kidney stones
  • sensitivity to sunlight
  • abnormal blood clotting
  • deafness
  • blood disorders
  • fatigue

However, these side effects are specific to certain types of antibiotics, so it is best to discuss their possibility with your doctor.

When to See a Doctor?

If you ever suspect a bacterial infection, it is best to see a doctor to discuss treatment options, including if antibiotics are needed. Your doctor can also discuss how long it will take for your symptoms to clear up.

While there are many medications available over the counter, oral antibiotics can only be obtained through a prescription. Because of this, it is crucial to see a doctor if you are experiencing any signs of infection or are generally feeling unwell.

If you finish your course of antibiotics and do not feel better, it is essential to discuss this with your doctor, as the antibiotic might not have killed the bacteria, necessitating a different antibiotic.

Get Help From an Online Doctor!

While oral antibiotics require a prescription, it is not necessary to go to a doctor’s office to obtain this. Online doctors are an excellent way to talk to your doctor about your symptoms and receive an antibiotic prescription if necessary. Through DrHouse, you can meet with a doctor in just 15 minutes, no matter where you are.

In Conclusion

Antibiotics are a standard treatment for bacterial infections. With hundreds of antibiotics available, they can treat a range of infections, although each antibiotic works best for a particular type of bacteria.

Antibiotics begin working as soon as you take them. Still, your symptoms may take a few days to improve as the antibiotics work against the bacteria causing the infection. It is important to continue taking your antibiotic, even if you don’t think it’s working, as discontinuing it early can increase the risk of antibiotic resistance.

All oral antibiotics must be prescribed, but it is possible to get an antibiotic without going to a doctor. With an online doctor, such as those found using the DrHouse app, you can meet with a doctor from the comfort of your home to discuss your symptoms and receive a prescription.


Content on the DrHouse website is written by our medical content team and reviewed by qualified MDs, PhDs, NPs, and PharmDs. We follow strict content creation guidelines to ensure accurate medical information. However, this content is for informational purposes only and not a substitute for professional medical advice, diagnosis, or treatment. For more information read our medical disclaimer.

Always consult with your physician or other qualified health providers about medical concerns. Never disregard professional medical advice or delay seeking it based on what you read on this website.

If you are experiencing high fever (>103F/39.4C), shortness of breath, difficulty breathing, chest pain, heart palpitations, abnormal bruising, abnormal bleeding, extreme fatigue, dizziness, new weakness or paralysis, difficulty with speech, confusion, extreme pain in any body part, or inability to remain hydrated or keep down fluids or feel you may have any other life-threatening condition, please go to the emergency department or call 911 immediately.



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