Antibiotics serve as a powerful remedy against infections. And while most people take them with no questions asked, thoughts like “do antibiotics make you tired?” or “do antibiotics make you sleepy” would have likely crossed the minds of the curious. But do they? 

What Do Antibiotics Do?

Antibiotics are medications used to fight bacterial infections by killing or decreasing the growth of bacteria in the body (which is why they’re also called antibacterials)

Penicillin, the first considered antibiotic, was discovered by Alexander Fleming, then a professor of Bacteriology at St. Mary’s Hospital in London, in 1928. But it wasn’t the next decade that German biochemist Gerhard Domagk formulated the sulfonamide Prontosil, the first commercially available antibacterial.

Before antibiotics, many children died from diseases like bacterial meningitis and strep throat. Most of those who did live had severe and lasting physical and mental disabilities throughout their lives. Streptococcus pyogenes also caused half of all post-birth deaths and expedited death from burns.

Antibiotics usually come in the form of::

  • Oral tablets, capsules, or liquid/syrup antibiotics – These are the most common antibiotic forms and are usually used to treat most types of mild to moderate infections in the body.
  • Topical antibiotics – Antibiotic creams, lotions, sprays, and drops are often used to treat skin, eye, or ear infections
  • Injectable antibiotics – these can be given as an injection or through a drip directly into the blood or muscle and are used for more serious infections.

Antibiotics begin to work right after you start taking them. Improvement in patients with bacterial infections often appears within one to three days, but how quickly one recovers after antibiotic treatment varies. It also depends on the type of infection being treated for. But ultimately, the doctor will prescribe the ideal length of treatment and correct antibiotic type for your condition.

Doctors advise finishing the complete antibiotic regimen, even if you feel better already after a few days of treatment, to fully resolve your infection and prevent antibiotic resistance. Antibiotic resistance occurs when certain antibiotics can no longer eliminate the bacteria in the body. In some cases, this can mean there are no effective treatments for certain conditions.  

Using the wrong antibiotic, dosage, skipping, or taking it longer or shorter than prescribed might contribute to bacterial resistance. Don’t stop your antibiotic regimen early unless a medical professional recommends you to do so.

Do Antibiotics Make You Tired & Sleepy? – Side Effects 

Some people may feel a little tired or sleepy after taking their antibiotics. As of now now, science doesn’t really know why it happens. 

One reason is that it could signify the antibiotics taking effect and treating the infection. Studies show that antibiotics’ more common side effects include nausea, vomiting, and diarrhea, which indicate the antibiotics at work kill both the good and bad bacteria in the body, which could lead to stomach issues and even dehydration. 

On the one hand, it could also be a rare but serious side effect of the particular antibiotic being used. The following antibiotics have been noted to cause such effects:

  • Amoxicillin – A penicillin antibiotic used to treat bacterial infections, including bronchitis and pneumonia. Fatigue and sleepiness are one of this antibiotic’s rarer side effects. Amoxicillin is available under brand names like Amoxil and Moxatag, among others. 
  • Azithromycin – Azithromycin is used to treat many infections caused by bacteria, such as respiratory and skin infections. Brand names include Z-Pak, Zithromax, and Zmax.
  • Ciprofloxacin – Ciprofloxacin belongs to a class of drugs called quinolone antibiotics and is used to treat more serious infections like chest infections (pneumonia) or ones that have been previously resistant to other antibiotics. This antibiotic is sold under brand names like Cipro and Proquin.

If the fatigues and drowsiness become frequent even after the regimen, it’s best to consult your doctor immediately. Your doctor may prescribe a different treatment or discontinue the regimen altogether. 

Other Side Effects

As with all medications, antibiotics tend to cause a few side effects.

  • Digestive problems
  • Headaches
  • Fungal infections
  • Shortness of breath
  • Photosensitivity
  • Depression and anxiety

Recent studies show that antibiotics can lead to fungal infection by disrupting the gut’s immune system. Antibiotics can make women more likely to get a vaginal yeast infection, also known as vulvovaginal candidiasis (Men can also get candidiasis). Pregnant women or those with weakened immune systems are also more likely to get infected. 

In some cases, some people have an allergic reaction or be hypersensitive to antibiotics, as some new researches show, especially penicillin and cephalosporins, which often results in rashes or hives. In rare cases, this can lead to serious allergic reactions or anaphylaxis, which warrants a prompt trip to the emergency room.  


Antibiotics may also interfere with other medications or drugs, such as:

  • Antacids
  • Antihistamines
  • Anti-inflammatory/anti-fungal drugs
  • Blood thinners
  • Diuretics
  • Muscle relaxants

Interacting with other drugs could cause the drug to be more or less effective or cause unexpected side effects.

The Best Time To Take Antibiotics

Antibiotics are usually taken three times a day and must be taken at set times so that their effect is spread out evenly over the day. For example, you could plot your antibiotic intake at around 6 a.m., 2 p.m., and 10 p.m. for an antibiotic that needs to be taken every 8 hours.

Some antibiotics differ on whether one should eat or not before ingesting them. For example, doctors recommend taking antibiotics like penicillin and flucloxacillin before meals, while metronidazole, trimethoprim, doxycycline, and nitrofurantoin are usually taken after eating.  

However, amoxicillin and ciprofloxacin are safe to ingest before or after a meal. 

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While antibiotics are critical and effective in treating various bacterial infections, some people may experience rarer side effects, such as constant tiredness or sleepiness. However, more studies are needed to establish if these signify the antibiotics at work or if they could be a sign of something more serious.

Consult your doctor if the fatigue, sleepiness, or other side effects continue or worsen. They can weigh on the situation and deem if you should continue with the treatment or drop it altogether. 

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