How Long Do Antibiotics Stay In Your System

You must have heard a lot about antibiotics. Am I right? Whenever someone falls ill suddenly everyone starts prescribing antibiotics as if they are doctors themselves. It may sound funny but this is today’s reality.

In today’s article, we’ll be talking all about antibiotics. Generally speaking, antibiotics are medicines that are used to treat a wide variety of infections and diseases which are caused by bacteria.

Antibiotics have played a major role in saving millions of lives since their very first introduction. Doesn’t that sound interesting? So stay tuned to the rest of the article and don’t miss even a single piece of information regarding antibiotics.

What are antibiotics?

Antibiotics is made up of two words, Anti means against while bios means life. As a whole it literally means ‘life-killing’. 

Actually these are the drugs or medicines which are used for the treatment of bacterial infections like the infections of ear, throat and urinary tract.

The other name for antibiotics is “ antibacterial” 

Types of antibiotics:

Two most basic types of antibiotics are

Bactericidal: The antibiotics that kill the bacteria commonly by stopping the synthesis of their cell wall, are termed as bactericidal.

Bacteriostatic: The antibiotics that inhibit/ stop the further growth and reproduction of bacteria are termed as the bacteriostatic.

Antibiotics are further classified into various classes.

First Antibiotic:

Penicillin was the first discovered antibiotic. Before the discovery of penicillin, about thirty percent of all the deaths were caused by bacterial infections.  Further many deadly diseases were cured by them which included the meningitis and syphilis.  

The half life of penicillin is about 1.4 hours and it completely eliminates from the body in 7.7 hours.  

How Long Do Antibiotics Stay In Your System? 

  As all the Antibiotics and their half-lives are different so they stay for different times in different bodies. The time duration of an antibiotic in one’s body may depend upon various factors which are given as under:


1: Depends upon the type of antibiotic:

How long does an antibiotic reside a system mainly depends on the type of antibiotic being used. It may be bactericidal or bacteriostatic. Its rate of action may be instant or slow. So it all depends upon the type of Antibiotic being used.

2: Depends upon the half life of antibiotic:

“ Half-life of an antibiotic is the time taken by it to decrease to One-half of its original concentration ( which was taken initially)”-

It is different for different drugs and antibiotics .Most of the medicines being used have an average half life of 24 hours. It means half of their initial concentration is decreased. 

For example amoxicillin is an antibiotic having a half life of about one hour ( 61.3min) . About 60 percent of its initial concentration is removed through the urine within 6 -8 hours. 

It takes 4-5 half lives of a drug to be completely (94 to 97% ) removed by the body.

3: Depends upon your Metabolic rate:

When a drug is ingested ,it breaks down into small molecules and then absorbs in the body . The un-absorbed particles are eliminated from the body through urine. The metabolic rate of a person plays an important role in this regard. Higher the greater metabolic rate more is the faster removal of Antibiotics from the body. So Antibiotics will stay in the system for a shorter time period. 

4: Renal and hepatic functional ability:

As we know that kidney and liver are the important organs involved in elimination of waste products from the body . So the time span of a drug in the body is also related to the functional ability of its organs to eliminate waste products. The sooner the kidney and liver will remove the waste , the shorter will be the time period of Antibiotics in the body .

5: Depends upon the dose of antibiotic:

The larger dose may not be easily absorbed. It is not removed immediately and stays longer. So it is also a factor in this regard. By

6: Mode of Action of Antibiotic:

More is the effectiveness of the antibiotic better will be the mode of action. The action of various antibiotics varies from one another.

7: Type of infection: 

Some infections are mild while some are more infectious and destructive. So, type of infection is also an important factor in determining the timespan of antibiotics in the body. If the infection is serious or destructive then Antibiotics will act accordingly .

How long an antibiotic takes to get into the body?

As an antibiotic is ingested in the body , it starts its working process. It targets the bacteria and kills them. Sometimes it may change their DNA or RNA in their genetic composition to stop them from reproduction. Some antibiotics may target the cell membranes and cell walls of the bacteria. They inhibit the synthesis of their cell walls and cell membranes. This affects their growth and reproduction.

Do antibiotics kill viruses?

The answer is a clear No ,viruses and bacteria are two separate types of microorganisms. So Antibiotics only kill or inhabit the growth of bacteria. For viral infections we use antiviral drugs like in flu and cold.

Side effects of Antibiotics:

There may be various side effects caused by antibiotics which may include

  • Difficulties in digestion
  • Nausea is the basic sign of its side effects.
  • Vomiting can also be a sign.
  • Diarrhoea is its most common side effect.

Once you stop taking any Antibiotic its side affects will vanish within some days. 

Dairy products should not be taken after ingesting antibiotics because they contain calcium which can dampen the effect on Antibiotic . Dairy products may assist in causing side effects.

Antibiotic Resistance:

After starting the antibiotic course few changes occur in the system of an individual. Taking antibiotics leads to the killing of sensitive bacteria. The leftover bacteria are surviving ones. The surviving bacteria become resistant to the antibiotics and the action disappears.

Why and how it happens? The answer to this question is that they become exposed to the drug and survive, later on they change their genetics to produce particular drug resistant genes. These genes help them to fight that Antibiotic and become resistant to it .The whole process is termed as antibiotic resistance.

Annually about 2 million people are infected and almost 23000 die due to resistant bacteria. 


In fact Antibiotics are a great blessing . Thousands of people use them and get cured. Many years back, Antibiotics were used by the soldiers to treat their infections and wounds. Hundreds of new Antibiotics have been found and prepared in the laboratory. They cover a broad spectrum and are used worldwide today. The discovery of Antibiotics began a new era of medicine. 

Take your medicine according to your prescription and for further details contact your doctor!

By Caitlyn

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