Do Antibiotics Make You Tired?

multiple antibiotic pills on a blue background

Do Antibiotics Make You Tired & Lethargic?

It’s not unheard of that antibiotics make people tired. There’s been much scientific research to support or refute these claims. It can be hard to tell if fatigue is a side effect of antibiotics, the immune system fighting off infections, other medications, other illnesses, or lifestyle factors.

Since some research shows antibiotics can induce sleepiness and fatigue, it’s essential to understand what antibiotics do and which antibiotics can make someone sleepy. First, it’s necessary to understand what antibiotics do.

What Antibiotics Actually Do 

Antibiotics, also known as antibacterials, kill bacteria or stop bacteria from reproducing. Antibiotics enter the bloodstream from the digestive tract when taken orally. The antibiotics make their way to the bacteria and attack the bacteria’s cells or surround the bacteria so it can’t multiply itself. This process gives support to the immune system to fight off infections.

Antibiotics only treat infections caused by bacteria. Common examples include E. coli, strep throat, a urinary tract infection, and life-threatening sepsis. Antibiotics can’t treat infections caused by viruses. Common examples include the flu, a cold, a sore throat, or even a lung virus.

Some antibiotics are engineered to attack specific bacteria, while other antibiotics, known as broad-spectrum antibiotics, attack many different types of bacteria, including good bacteria.

According to the Microbiology Society, antibiotics are any substance that stops growth or kills a bacterium. Antibacterials are forms of antimicrobials. 

Some antibacterials, like penicillin and cephalosporin, directly kill the bacteria. These are called bactericides. Other antibacterials, such as tetracycline and erythromycin, stop bacteria reproduction and growth, and these are called bacteriostatic.

Two other widely used antimicrobials are antiseptics and disinfectants. Antiseptics sterilize surfaces and skin and are mandatory during surgery. Disinfectants are used in hospitals and on non-living surfaces to kill different microorganisms.

detailed photo of red and white antibiotic pills

Types of Antibiotics

There are seven main groups of antibiotics. There are over 90 antibiotics that belong to these seven groups.

  • Penicillin: penicillin and amoxicillin
  • Cephalosporin: cephalexin
  • Fluoroquinolone: ciprofloxacin, levofloxacin, and ofloxacin
  • Macrolide: erythromycin, clarithromycin, and azithromycin
  • Sulfonamide: trimethoprim and co-trimoxazole
  • Tetracycline: doxycycline and tetracycline
  • Aminoglycoside: gentamicin and tobramycin

All of these antibiotics treat different types of infections.

The penicillin and macrolide classes of antibiotics are the most commonly prescribed antibiotics —specifically, amoxicillin— for skin conditions caused by staphylococci and streptococci.

Amoxicillin and penicillin treat middle-ear infections, sinus infections, respiratory infections, and kidney infections.

Fluoroquinolone antibiotics treat respiratory infections like bronchitis.

Cephalosporin antibiotics treat urinary tract infections and infections with the bladder.

Antibacterials like cephalexin can treat meningitis, pneumonia, and skin disorders. Doxycycline, tetracycline, and ciprofloxacin can treat sexually transmitted diseases like chlamydia and gonorrhea.

Since antibiotics can treat a broad range of bacterial infections, their overprescription has been noticed and studied. A study in 2015 showed a correlation between decision fatigue in doctors and overprescribing antibiotics.

To counter this, the Center for Disease Control and Prevention (CDC) reports that they would implement measures to reduce antibiotic prescription by 50%.

Yet during COVID-19, antibiotic prescriptions were up 71% from the original 48% decrease from 2019 and 2020, the NHS reported.

There are negative repercussions to the overprescribing of antibacterials. When antibacterials are overused, bacteria evolve and become resistant to antibiotics over time, especially to penicillins. Because of antibiotic resistance, it’s essential to take antibiotics as prescribed.

Don’t stop taking antibiotics even if bacterial infection symptoms disappear. Discontinuing antibiotics earlier than instructed results in antibiotic resistance; the infectious bacteria can remain despite no signs.

white pills spilling out of a pill bottle

Which Types Make You Sleepy

Out of the seven main classes of antibiotics and over hundreds of different kinds of antibiotics, only three kinds cause fatigue as a side effect.

These three are amoxicillin, azithromycin, and ciprofloxacin, with the brand names Moxatag, Zithromax, and Cipro-XR. When azithromycin is causing fatigue, doctors can switch this antibiotic to clarithromycin (Biaxin). Ciprofloxacin is an ideal option for patients allergic to penicillin. The exact science of why these three cause tiredness and low energy is unknown.

Often, most patients don’t have a say in choosing the antibacterial. Doctors take tests to find the bacteria and choose an antibacterial, and some antibiotics are more effective than others.

Yet, depending on dosing and prices, patients and doctors can work out an affordable and effective antibacterial treatment.

Other Medications Affecting Energy Levels 

Many other medications outside of antibacterials affect energy levels. Other medications known to cause sleepiness and fatigue are high blood pressure medications such as Prinivil, Norvasc, Lasix, Toprol, and Tekturna.

Blood pressure causes fatigue by slowing down the heart and the central nervous system. This lowers pressures inside of blood vessels yet also causes a depressing effect on the nerves, causing relaxation and even sedation. Blood pressure medication also has a diuretic effect which depletes the body of electrolytes it needs.

Medications to manage cholesterol can also affect energy levels. Doctors prescribe Lipitor, Crestor, Zocor, and Tricor to treat high cholesterol. These medications are classified as statins and fibrates. Statins and fibrates stop muscle growth and interfere with energy production in cells. This results in muscle weakness, muscle aches, and muscle fatigue that spreads throughout the body.

Benzodiazepines are anxiety medications known to treat anxiety disorders. Benzodiazepines directly cause sleepiness and lethargy. Xanax, Valium, Ativan, and Klonopin are brands of benzodiazepines to reduce anxiety and stress, treat insomnia, and even prevent seizures. Benzodiazepines, like blood pressure medications, target the central nervous system, causing a depressing effect.

Finally, opioid pain medicines like OxyContin, Percocet, Percodan, and Vicodin act like endorphins to control pain. Opioids disrupt the sleep cycle. They can also cause sleep abnormalities and lead to restless nights waking up during sleep. Sleep abnormalities from opioids include sleep apnea, disordered breathing, and reduced REM sleep.

woman wearing glasses and yawning

Lifestyle Factors Affecting Fatigue

Before concluding that antibiotics are causing fatigue, it’s essential to rule out what else could be causing low energy throughout the day. 

Many factors play into chronic fatigue, like stress, diet, and physical activity. Nutritionist Resource UK lists psychological causes, medical causes, and dietary causes affecting energy levels.


Experts at Biocare UK say that the human body isn’t meant to go through too much stress. Prolonged stress uses energy from the body and depletes the body of needed nutrients. Constant pressure produces higher levels of cortisol that negatively impact sleep. Cortisol is what makes people alert and on edge. Too much cortisol comes in hand with a spike of adrenaline — disrupting sleep more and making it uncomfortable to fall and stay asleep. 

Stress can cause fatigue by suppressing the immune system, and it can also reduce the immune system’s ability to use energy. Thyroid function is reduced by stress as well. The thyroid balances hormones that impact energy levels. Stress suppresses thyroid hormones, thus making someone sluggish and tired.

Along with the immune system and thyroid, stress also affects the endocannabinoid system (ECS). The ECS is a biological system that produces lipids that balance energy levels and immune responses.

Physical signs of stress include body aches, stomach discomfort, muscle tension, insomnia, nightmares, and high blood pressure. 


Our nutritional choices can be a source of energy and lethargy. Some foods slow, inflame, and bloat the body, while other foods energize and enhance bodily functions.

Added sugar can be a cause of chronic fatigue and has little to no nutritional benefit while giving a short energy boost. This temporary energy boost results in a sugar crash, leaving someone even more tired.

Avoid processed foods that are carbohydrate heavy and bleached to fight fatigue. Too many processed grains can lead to over-fullness, slowness, and constipation. White rice, white bread, and pasta are foods with little nutritional value.

Caffeine in coffee, energy drinks, and certain teas (like black tea and green tea) can boost energy. Caffeinated beverages are known for a short jolt of energy that causes caffeine crashes and builds up a caffeine tolerance over time, making someone tired and sleepy.

tired man and woman sitting at a messy desk

Physical Activity

A regular exercise routine or regular activity throughout the day can enhance sleep at night. Yet, excess physical activity causes low energy.

Exercise depletes nutrient-rich energy sources in the body. No rest between workouts can cause muscle weakness and excess stress on joints. This extra stress on the body with no recovery causes aches and pains, leading to an exhausted body.

On the other hand, too little physical activity can lead to chronic fatigue. An inactive lifestyle causes muscle weakness, muscle fatigue, some muscle loss, and mineral depletion.


It might sound obvious, but practicing bad sleep habits can cause fatigue — too little sleep, too much sleep, and inconsistent sleep affects energy levels.

The body has an internal clock that tells it when to wake up and sleep. The internal clock is called the circadian rhythm. The time of day and levels of light and darkness affect natural circadian processes. Messing up the circadian rhythm has negative impacts on health: researchers at John Hopkins University say that oversleeping can cause psychological exhaustion, leading to depression.

Why Do Antibiotics Make You Tired?

When fighting a bacterial infection, especially with an antibiotic, feeling tired and lethargic is expected. When the immune system and antibiotics work together to fight infections, the body uses its energy storage. 

Antibacterials kill the good bacteria our bodies need along with the harmful bacteria. With less healthy bacteria in the gut, nutrient absorption becomes less effective. This process takes a lot of energy from the body. Nutrients that would be absorbed and used throughout the day are depleted. Nutrient depletion leads to dehydration and lethargy. Nutrient depletion while taking antibiotics is one of the most significant factors of fatigue.

tired older woman

Common Side Effects of Antibiotics

Every medication and every supplement has the potential of an adverse effect. Most often, side effects are mild. Official sites such as Mayo Clinic state that a common side effect of antibacterials is diarrhea; it’s such a common side effect that Mayo Clinic reported 1 in 5 people who take antibiotics get diarrhea.

The term is known as antibiotic-associated diarrhea. In rare cases, antibiotic-associated diarrhea can be so severe that a patient must stop using antibiotics or switch to a different class of antibiotics. Due to its typically mild and non threatening effects, there is no cure or treatment for antibiotic-associated diarrhea.

Much research has shown the effect of antibacterials on gut bacteria and gut microbiota. This can lead to digestion problems, inflamed stomach lining, and loose stools. Other side effects of antibiotics include headaches, muscle aches, and sensitivity to the sun.

Oral thrush is a common side effect of taking antibiotics. Thrush is a fungal infection. Fungal bacteria known as Candida lives in the mouth and throat and is a type of yeast. In a healthy person, good bacteria stop the overgrowth of Candida. Antibiotics kill good bacteria, too, resulting in a higher chance of Candida yeast overgrowth.

The NHS reports that 1 in 15 people have an allergic reaction to antibiotics- most notably, penicillin. A possibly fatal effect of a penicillin allergy is anaphylaxis. Penicillin and other antibacterial allergy signs could include skin rash, hives, and itchy skin,  swelling, wheezing, and a fever. Antihistamines such as Benadryl can tame mild antibiotic allergic reactions.

One study even showed antibiotics cause convulsions in some patients.

Possible Drug Interactions

A doctor asks the patient if they’re taking any other medications before prescribing a drug. This is because most prescription and over-the-counter medicines interact with other medicines taken. The side effects can range from severe – causing liver failure – or a bit less worrying and making the drug not as effective. Drug interactions can cause the medication to overwork or not work at all.

Antibacterials are no exception. shows a total of 37 drug interactions with amoxicillin alone. Typical interactions with antibiotics like amoxicillin include alcohol, aspirin, Tylenol, Benadryl, etc.

How To Fight Off Antibiotic Induced Fatigue

Antibiotics are a helpful and life-saving medicine, and despite uncomfortable symptoms that can come with antibiotics, there are no alternatives to taking them. Possible lethargy and sleepiness don’t have to be an overbearing side effect of taking antibiotics. There are methods to mitigate the intensity of sleepiness. 

person holding sleeves of antibiotic pills

B Vitamins

B vitamins are essential nutrients that have unique functions for the body. B vitamins are an essential component of bodily health: from skin, nails, and hair growth to cardiovascular health. There are eight types of B vitamins. Of all eight B vitamins, vitamins B6 and B12 are ideal for restoring energy levels.

B vitamins restore energy and nutrients to the body. Some supplements mix all eight B vitamins together. These mixtures are called vitamin B complexes. Taking vitamin B complex when taking antibiotics enhances energy use in the body.

Unless B-complex supplements are available, it’s essential to eat foods rich in B vitamins to get a healthy serving of B vitamins. Most B vitamins come together in food. Vitamin B6, or pyridoxine, is found in chickpeas, salmon, and potatoes. Vitamin B12, or cobalamin, is found in clams, yogurt, salmon, and beef liver.

During periods of physical and mental stress, the body loses B vitamins. Eating vitamin B-rich foods or vitamin B supplements reduces stress and combats antibiotic symptoms.

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Omega-3 Fatty Acids

According to the National Institute of Health (NIH), omega-3 fatty acids are “important components of the membranes that surround each cell in your body.” Omega-3 fatty acids are essential for the brain, the eyes, and reproductive cells. The human body can’t make omega-3 fatty acids, so it gets these essential acids from foods.

Dietary supplements like fish oil provide concentrated amounts of omega-3 fatty acids. Seafood and flaxseed are the highest sources of omega-3 fatty acids. Seafood such as tuna, sardines, mackerel, and salmon offer large amounts of these essential fatty acids.

The body uses the three primary acids found in omega-3s to give energy to cells. The three primary acids are alpha-linolenic acid (ALA), docosahexaenoic acid (DHA), and eicosapentaenoic acid (EPA). Taking omega-3 fatty acids decreases fatigue, balances mood swings, and helps blood circulation.

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UPMC reports that “people who take probiotics are 42 percent less likely to develop” antibiotic symptoms, including that of diarrhea. Probiotics are live microorganisms that live in the body. These microorganisms are a mixture of bacteria and yeast. Probiotics promote a healthy gut which gives a plethora of health benefits.

Research has found that particular probiotic strains can reduce antibiotic symptoms. Since antibiotics kill bacteria, and probiotics grow bacteria, taking probiotics restores balance to the body. In the form of kefir or other fermented milk products, probiotics give the body calories to burn for energy- All the energy needed to fight bacterial infections, gain power, and promote a healthy body.

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Replenish Electrolytes

A study published in 2018 by the Department of Internal Medicine of BronxCare Hospital Center showed that antibiotics can cause electrolyte disturbances. A patient had hypokalemia (potassium deficiency), possibly induced by the penicillin antibiotic Nafcillin.

An antibiotic-induced electrolyte disturbance happens because antibiotics can contain high amounts of potassium and sodium. Other electrolyte disturbances such as hyperkalemia (too much potassium) can lead to fluid build-up in the body.

Too little or too much sodium can cause fatigue and brain fog. It’s necessary to drink natural fruit juices, bone broths, soups, or coconut water to replenish electrolytes and reduce fatigue.

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Speak To A Doctor

The best advice is to speak with a primary care doctor or specialist about what you can do to mitigate sleepiness from antibiotics. A primary care doctor or specialist will have insight into personal needs and how to overcome symptoms.

Any side effects of antibiotics, including fatigue, must be discussed with a doctor. Fatigue and low energy can be symptoms of an underlying disease or problem.

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