Table of ContentsView AllTable of ContentsHow Long Do Antibiotics Stay in Your System?Antibiotic Half-LifeOther Factors
Table of ContentsView All
View All
Table of Contents
How Long Do Antibiotics Stay in Your System?
Antibiotic Half-Life
Other Factors
Antibiotics can generally stay in your body for hours or even days, depending on your health status and the duration of your treatment.
This article will discuss how long different antibiotics will stay in your body after taking them.
Getty Images / Israel Sebastian
Most antibiotics start working right after you take the first dose. Each antibiotic may stay in your body for a different amount of time, as many different classes exist.
Several factors can influence how long an antibiotic stays in your system, including the type of antibiotic, how long you’re taking it, and your health.
Some common antibiotics, such as penicillin (e.g., amoxicillin) or ciprofloxacin, can stay in your body for up to 12 to 24 hours after your last dose.
Other antibiotics can stay in the body much longer. Zithromax (azithromycin), for example, can stay in the body for up to 14 days after the last dose.
If you have kidney problems, clearing the antibiotics from your body might take longer. Additionally, being on a longer-term antibiotic regimen may increase the time it lasts in the body.
Every Antibiotics Question You Have, Answered
What Does Antibiotic Half-Life Mean?
Depending on your height and weight, an antibiotic’s half-life may help determine how long it will stay in your body. Each antibiotic has a different half-life and can range from short half-lives of only an hour to half-lives over 68 hours before half of the drug has been eliminated from the body.
What Other Factors Affect How Long Antibiotics Stay in the Body?
Other factors crucial to the amount of time an antibiotic may stay in the body can include:
For this reason, the prescribed dosing for an adult versus a child might differ.
Depending on the specific medication given, it could last in the body as long as a few hours or up to a few days.
Different formulations are also available for antibiotics, which can affect absorption in the body. These include:
Still, the specific type of antibiotic and dose play the most important role in determining the amount of time the drug will stay in your system.
Types of Antibiotics
Antibiotics can be either bactericidal or bacteriostatic. Bactericidal antibiotics kill the bacteria, whereas bacteriostatic antibiotics prevent the growth of bacteria.
Examples of bacteriostatic antibiotics include the following:
Bactericidal antibiotics include:
Dosage and Administration
The dosage and administration of your antibiotic will vary depending on the specific illness or infection present in the body.
Common short-course antibiotic regimens can range anywhere from a few days to up to two weeks. Acute infections will likely only require oral or topical antibiotic forms. However, more severe infections may warrant intravenous (IV) antibiotics administered through the veins.
Your healthcare provider will determine your dose based on the type of infection and antibiotic. Dosing recommendations may also change for people with kidney problems and children.
Generally, large doses of antibiotics are not always the best form of treatment. The bacteria in our body may become resistant to these high doses of antibiotics, which later become too strong to treat with traditional antibiotics. Antibiotic resistance occurs when the germs or bacteria fight off the drugs designed to kill or suppress them.
The likelihood of antibiotic resistance has increased rapidly due to the poor use of antibiotics. The right dose and medication for the right bug or bacteria should always be discussed with your primary healthcare provider.
Summary
Antibiotics will always play a crucial role in treating infections. As with any drug, it will take some time to completely leave your body after taking it. The length of time antibiotics stay in your system will vary but usually last from a few hours to a few days.
Other factors, such as health status and type of antibiotic, can influence the drug’s clearance rate.
Talk to your healthcare provider if you have questions about your infection and antibiotic treatment.
Frequently Asked QuestionsGenerally, most antibiotics are safe to take on an empty stomach. While taking your dose with food can prevent stomach upset, most diets do not affect how long an antibiotic will stay in the body.Consumption of dairy products (e.g., cheese, yogurt, milk) could reduce how well certain antibiotics work. For example, you should take tetracyclines three hours before having any dairy products. Before starting treatment, ask your healthcare provider if dairy consumption will affect your particular antibiotic.Some antibiotics can be broken down in the liver. If you take other medications that are broken down in the liver, the antibiotic’s half-life could be affected.Always tell your healthcare provider about all your medications before starting a new treatment. They can inform you if any interactions are possible.
Frequently Asked Questions
Generally, most antibiotics are safe to take on an empty stomach. While taking your dose with food can prevent stomach upset, most diets do not affect how long an antibiotic will stay in the body.Consumption of dairy products (e.g., cheese, yogurt, milk) could reduce how well certain antibiotics work. For example, you should take tetracyclines three hours before having any dairy products. Before starting treatment, ask your healthcare provider if dairy consumption will affect your particular antibiotic.
Generally, most antibiotics are safe to take on an empty stomach. While taking your dose with food can prevent stomach upset, most diets do not affect how long an antibiotic will stay in the body.
Consumption of dairy products (e.g., cheese, yogurt, milk) could reduce how well certain antibiotics work. For example, you should take tetracyclines three hours before having any dairy products. Before starting treatment, ask your healthcare provider if dairy consumption will affect your particular antibiotic.
Some antibiotics can be broken down in the liver. If you take other medications that are broken down in the liver, the antibiotic’s half-life could be affected.Always tell your healthcare provider about all your medications before starting a new treatment. They can inform you if any interactions are possible.
Some antibiotics can be broken down in the liver. If you take other medications that are broken down in the liver, the antibiotic’s half-life could be affected.
Always tell your healthcare provider about all your medications before starting a new treatment. They can inform you if any interactions are possible.
The author would like to recognize and thank Jaycob Mathew Peña for contributing to this article.
10 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Hutchings MI, Truman AW, Wilkinson B.Antibiotics: past, present and future.Curr Opin Microbiol. 2019;51:72-80. doi:10.1016/j.mib.2019.10.008Food and Drug Administration.Amoxil label.Food and Drug Administration.Zithromax label.Baietto L, Corcione S, Pacini G, Perri GD, D’Avolio A, De Rosa FG.A 30-years review on pharmacokinetics of antibiotics: is the right time for pharmacogenetics?Curr Drug Metab.2014;15(6):581-598. doi:10.2174/1389200215666140605130935Halilovic J, Heintz BH.Antibiotic dosing in cirrhosis.Am J Health Syst Pharm. 2014;71(19):1621-1634. doi:10.2146/ajhp140031Tucker CE, Lockwood AM, Nguyen NH.Antibiotic dosing in obesity: the search for optimum dosing strategies.Clin Obes. 2014;4(6):287-295. doi:10.1111/cob.12076Levison ME, Levison JH.Pharmacokinetics and pharmacodynamics of antibacterial agents.Infect Dis Clin North Am. 2009;23(4):791-vii. doi:10.1016/j.idc.2009.06.008Centers for Disease Control and Prevention.Antibiotic use and antimicrobial resistance facts.Patel P, Wermuth HR, Calhoun C, et al.Antibiotics. In:StatPearls.Treasure Island (FL): StatPearls Publishing; 2023.Reis A, Joaquim J.Drug interaction with milk and the relevance of acidifying/alkalizing nature of food.Clinical Therapeutics. 2015;37(8); e67-e68.
10 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Hutchings MI, Truman AW, Wilkinson B.Antibiotics: past, present and future.Curr Opin Microbiol. 2019;51:72-80. doi:10.1016/j.mib.2019.10.008Food and Drug Administration.Amoxil label.Food and Drug Administration.Zithromax label.Baietto L, Corcione S, Pacini G, Perri GD, D’Avolio A, De Rosa FG.A 30-years review on pharmacokinetics of antibiotics: is the right time for pharmacogenetics?Curr Drug Metab.2014;15(6):581-598. doi:10.2174/1389200215666140605130935Halilovic J, Heintz BH.Antibiotic dosing in cirrhosis.Am J Health Syst Pharm. 2014;71(19):1621-1634. doi:10.2146/ajhp140031Tucker CE, Lockwood AM, Nguyen NH.Antibiotic dosing in obesity: the search for optimum dosing strategies.Clin Obes. 2014;4(6):287-295. doi:10.1111/cob.12076Levison ME, Levison JH.Pharmacokinetics and pharmacodynamics of antibacterial agents.Infect Dis Clin North Am. 2009;23(4):791-vii. doi:10.1016/j.idc.2009.06.008Centers for Disease Control and Prevention.Antibiotic use and antimicrobial resistance facts.Patel P, Wermuth HR, Calhoun C, et al.Antibiotics. In:StatPearls.Treasure Island (FL): StatPearls Publishing; 2023.Reis A, Joaquim J.Drug interaction with milk and the relevance of acidifying/alkalizing nature of food.Clinical Therapeutics. 2015;37(8); e67-e68.
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Hutchings MI, Truman AW, Wilkinson B.Antibiotics: past, present and future.Curr Opin Microbiol. 2019;51:72-80. doi:10.1016/j.mib.2019.10.008Food and Drug Administration.Amoxil label.Food and Drug Administration.Zithromax label.Baietto L, Corcione S, Pacini G, Perri GD, D’Avolio A, De Rosa FG.A 30-years review on pharmacokinetics of antibiotics: is the right time for pharmacogenetics?Curr Drug Metab.2014;15(6):581-598. doi:10.2174/1389200215666140605130935Halilovic J, Heintz BH.Antibiotic dosing in cirrhosis.Am J Health Syst Pharm. 2014;71(19):1621-1634. doi:10.2146/ajhp140031Tucker CE, Lockwood AM, Nguyen NH.Antibiotic dosing in obesity: the search for optimum dosing strategies.Clin Obes. 2014;4(6):287-295. doi:10.1111/cob.12076Levison ME, Levison JH.Pharmacokinetics and pharmacodynamics of antibacterial agents.Infect Dis Clin North Am. 2009;23(4):791-vii. doi:10.1016/j.idc.2009.06.008Centers for Disease Control and Prevention.Antibiotic use and antimicrobial resistance facts.Patel P, Wermuth HR, Calhoun C, et al.Antibiotics. In:StatPearls.Treasure Island (FL): StatPearls Publishing; 2023.Reis A, Joaquim J.Drug interaction with milk and the relevance of acidifying/alkalizing nature of food.Clinical Therapeutics. 2015;37(8); e67-e68.
Hutchings MI, Truman AW, Wilkinson B.Antibiotics: past, present and future.Curr Opin Microbiol. 2019;51:72-80. doi:10.1016/j.mib.2019.10.008
Food and Drug Administration.Amoxil label.
Food and Drug Administration.Zithromax label.
Baietto L, Corcione S, Pacini G, Perri GD, D’Avolio A, De Rosa FG.A 30-years review on pharmacokinetics of antibiotics: is the right time for pharmacogenetics?Curr Drug Metab.2014;15(6):581-598. doi:10.2174/1389200215666140605130935
Halilovic J, Heintz BH.Antibiotic dosing in cirrhosis.Am J Health Syst Pharm. 2014;71(19):1621-1634. doi:10.2146/ajhp140031
Tucker CE, Lockwood AM, Nguyen NH.Antibiotic dosing in obesity: the search for optimum dosing strategies.Clin Obes. 2014;4(6):287-295. doi:10.1111/cob.12076
Levison ME, Levison JH.Pharmacokinetics and pharmacodynamics of antibacterial agents.Infect Dis Clin North Am. 2009;23(4):791-vii. doi:10.1016/j.idc.2009.06.008
Centers for Disease Control and Prevention.Antibiotic use and antimicrobial resistance facts.
Patel P, Wermuth HR, Calhoun C, et al.Antibiotics. In:StatPearls.Treasure Island (FL): StatPearls Publishing; 2023.
Reis A, Joaquim J.Drug interaction with milk and the relevance of acidifying/alkalizing nature of food.Clinical Therapeutics. 2015;37(8); e67-e68.
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