Can Antibiotics Make You Shaky and Weak? Understanding the Link

October 14, 2025 •

5 min read

While most antibiotic side effects are mild, affecting digestion or causing a rash, some people may experience more unusual reactions, such as shakiness or weakness. Though less common, antibiotic-induced neurological effects are a recognized adverse event, making it important to understand how and why antibiotics might make you shaky and weak.

Quick Summary

Antibiotics can rarely cause shakiness (tremors) and weakness (fatigue) due to neurotoxic effects or gut microbiome disruption. Contributing factors include specific drug classes and pre-existing conditions like renal impairment, but the infection itself is often the cause of fatigue.

Key Points

Rare but Possible Side Effect: Shakiness and weakness can be rare, but known, side effects of certain antibiotics, often linked to neurotoxic effects or systemic disruptions.
Underlying Infection is a Factor: The fatigue and weakness you feel while taking antibiotics may simply be your body's response to fighting the infection itself, rather than a side effect of the medication.
Specific Antibiotics Carry Higher Risks: Antibiotic classes like fluoroquinolones and tetracyclines have been documented to cause neurological side effects, including tremors.
Risk Factors Exist: Patients with pre-existing conditions like renal impairment, advanced age, or those taking multiple medications are at a higher risk of experiencing neurological side effects.
Seek Medical Advice for Severe Symptoms: If you experience severe weakness, persistent tremors, or other alarming neurological symptoms, contact your doctor immediately.
Gut Health Plays a Role: Antibiotics disrupt the gut microbiome, which can affect energy levels. Probiotics can help restore balance and may mitigate some fatigue.
Follow Prescribed Regimen: Always take antibiotics exactly as prescribed and complete the full course unless instructed otherwise by a healthcare provider.

Understanding the Link Between Antibiotics, Shakiness, and Weakness

When prescribed antibiotics to fight a bacterial infection, most patients focus on the benefits of overcoming their illness. However, for a small number of people, the medication can trigger unexpected side effects, including feelings of shakiness (tremors) and unusual weakness or fatigue. It is crucial to distinguish between the natural exhaustion that comes with fighting an infection and a specific adverse reaction to the medication itself. The causes of these symptoms are varied, ranging from direct neurotoxic effects to the body's overall response to both the illness and the treatment.

How Antibiotics Can Affect the Body's Systems

Several mechanisms can lead to the sensations of shakiness and weakness observed during or after antibiotic treatment. Some are related to the medication's effect on the central nervous system, while others are a consequence of systemic changes within the body.

Neurotoxic Effects

Certain antibiotics have the capacity to cross the blood-brain barrier, leading to a variety of neurological disturbances. The risk of these effects is often heightened in patients with renal impairment, which affects how the drug is cleared from the body, or at higher doses. Examples of these neurotoxic effects include:

Tremors and myoclonus: Involuntary muscle contractions or shaking, which can occur with classes like beta-lactams and fluoroquinolones.
Encephalopathy: A form of brain dysfunction that can manifest as confusion, seizures, or tremors.
Serotonin Syndrome: A rare but serious reaction caused by interactions between certain antibiotics (like linezolid and some fluoroquinolones) and other medications, particularly antidepressants. Symptoms can include tremors, rigidity, and agitation.

Disruption of the Gut Microbiome

Antibiotics are designed to kill bacteria, but they do not discriminate between harmful and beneficial strains. This can significantly disrupt the gut's delicate balance of bacteria, known as the microbiome. This disruption can have wide-ranging effects on the body's energy levels and overall well-being, contributing to feelings of fatigue and weakness. Restoring the gut flora through probiotics can sometimes help mitigate these side effects.

Allergic Reactions and Jarisch-Herxheimer Reaction

In some cases, tremors and weakness can be signs of a more severe systemic issue. A serious allergic reaction (anaphylaxis) can cause weakness, shaking, and dizziness, requiring immediate medical attention. Another rare possibility is the Jarisch-Herxheimer reaction, which occurs when antibiotics kill large numbers of bacteria, releasing toxins that trigger a temporary worsening of symptoms, including fatigue. This is most often seen in treatments for infections like syphilis or Lyme disease.

Antibiotic Classes Linked to Shakiness and Weakness

While these side effects are not universal, certain classes of antibiotics have been more frequently associated with tremors or fatigue:

Fluoroquinolones (e.g., Ciprofloxacin): Linked to fatigue, weakness, dizziness, and more serious neurological issues like tremors.
Tetracyclines (e.g., Doxycycline): Case reports have documented medication-induced tremors.
Beta-lactams (e.g., Penicillins, Cephalosporins): Associated with neurological side effects, including myoclonus and seizures, particularly at high doses or in patients with kidney problems.
Macrolides (e.g., Azithromycin, Erythromycin): Fatigue has been reported as a side effect, although it is considered rare.
Glycopeptides (e.g., Vancomycin): Fatigue can affect up to 5% of people receiving intravenous vancomycin.

Who Is Most at Risk?

Certain factors can increase an individual's susceptibility to antibiotic side effects, including shakiness and weakness.

Older Adults: Reduced immune function, a slower metabolism, and other health conditions can increase the likelihood of side effects.
Patients with Renal or Hepatic Impairment: Because most antibiotics are cleared by the kidneys or liver, impaired function can lead to toxic drug levels in the blood, increasing the risk of neurotoxicity.
Patients with Pre-existing CNS Conditions: Those with pre-existing neurological disorders may be more vulnerable to drug-induced neurotoxicity.
Taking Multiple Medications: Drug interactions, such as those that can lead to serotonin syndrome, are a risk factor for neurological symptoms.

How to Manage and What to Do

If you experience shakiness or weakness while on antibiotics, it is important to address the situation properly. The first step should always be to consult your healthcare provider. Do not stop the medication on your own, as this can worsen the infection.

Comparison of Potential Causes


Symptom	Likely Cause	Additional Context
Fatigue/Weakness (Mild)	The infection itself or general systemic stress	Your body is using energy to fight off the illness.
Fatigue/Weakness (Moderate)	Disrupted gut microbiome	Killing off beneficial bacteria can impact energy levels.
Fatigue/Weakness (Severe)	Rare drug side effect or complication (e.g., C. diff infection)	Contact your doctor if it interferes with daily life.
Shakiness/Tremors (Mild)	Medication side effect, especially with specific drugs or high doses	May resolve after the course is finished or with a dosage change.
Shakiness/Tremors (Severe)	Neurotoxic effect or drug interaction (e.g., Serotonin Syndrome)	Requires immediate medical attention.

Managing Symptoms

Prioritize Rest: Give your body the time and energy it needs to recover from the infection.
Stay Hydrated: Dehydration can exacerbate fatigue and weakness. Drink plenty of water throughout the day.
Balanced Diet: Eating nutritious meals can support your energy levels and help restore gut health.
Consider Probiotics: Probiotic foods (yogurt, kefir) or supplements can help replenish good gut bacteria. Take them a few hours away from your antibiotic dose.
Avoid Alcohol and Caffeine: These can interfere with sleep and hydration, worsening fatigue.

Conclusion

Experiencing shakiness or weakness while taking antibiotics, though not a common side effect, is a possibility that warrants attention. Often, fatigue is a normal part of the body's battle against an infection. However, certain factors, including specific drug classes and pre-existing health conditions like kidney impairment, can increase the risk of more direct neurological effects such as tremors or encephalopathy. Promptly communicating any concerns with a healthcare provider is essential for determining the cause and ensuring safe, effective treatment. If severe symptoms occur, immediate medical evaluation is necessary.

For more information on antibiotic side effects and safety, you can consult resources like the Cleveland Clinic.

Glossary of Terms

Neurotoxicity: Damage to or impaired function of the central or peripheral nervous system caused by a substance.
Tremor: An involuntary, rhythmic muscle contraction and relaxation, involving oscillations or twitching movements of one or more body parts.
Myoclonus: A quick, involuntary muscle jerk, contraction, or twitch.
Encephalopathy: Any diffuse disease of the brain that alters brain function or structure.
Gut Microbiome: The community of microorganisms (bacteria, fungi, viruses) living in the human gut.
Jarisch-Herxheimer Reaction: A short-term, whole-body inflammatory response that occurs when a large amount of toxins are released from dying bacteria during antibiotic treatment, most common for infections like syphilis or Lyme disease.

Frequently Asked Questions

Feeling tired and weak while on antibiotics is common and can be due to several reasons. Often, it's a normal symptom of your body fighting the underlying infection. Additionally, antibiotics can disrupt your gut microbiome, affecting your overall energy levels. In rare cases, fatigue can be a direct side effect of certain antibiotics, like vancomycin, azithromycin, or ciprofloxacin.

While it's a less common side effect, some antibiotics have been associated with drug-induced tremors. These include fluoroquinolones (like Cipro), tetracyclines (like doxycycline), and certain penicillins and cephalosporins, especially at high doses or in patients with renal impairment.

Mild shakiness or weakness is usually not dangerous but should be monitored. However, severe symptoms, especially when accompanied by confusion, high fever, or seizures, could indicate a serious neurological side effect like encephalopathy or serotonin syndrome and require immediate medical attention.

First, contact your healthcare provider to report the symptoms. They can help determine if it's a side effect or related to your illness. Do not stop taking the medication without consulting your doctor. Ensuring you get plenty of rest, stay hydrated, and eat well can also help manage mild symptoms.

Yes, probiotics can be helpful. Since antibiotics can disrupt the balance of 'good' bacteria in your gut, which can contribute to fatigue, taking probiotics can help restore this balance. It's recommended to take probiotics a few hours away from your antibiotic dose to maximize their effectiveness.

While shakiness isn't a primary symptom of a typical allergic reaction, severe allergic reactions (anaphylaxis) can cause weakness and a sense of feeling unwell, which could be associated with some trembling. Other signs like hives, swelling, and difficulty breathing are more definitive.

In most cases, if the shakiness or weakness is a direct side effect of the antibiotic, it will resolve once the medication course is completed and the drug is cleared from your system. However, if symptoms persist, it is important to follow up with your doctor.