Feeling constantly tired might have less to do with your schedule and more to do with what’s sitting in your medicine cabinet
Feeling worn out, sluggish, or like you need a nap by mid-morning? Before you blame your age or your schedule, it is worth checking the labels on your medicine cabinet. Fatigue is one of the most frequently reported side effects of both prescription and over-the-counter drugs, yet it often goes unrecognized as the culprit because it overlaps so naturally with how busy or stressed life already feels.
Research shows that nearly half of older adults regularly take medications that list somnolence as a possible adverse effect, and those using three or more of these drugs are nearly twice as likely to report excessive sleepiness. Knowing which categories of medications are most likely to drain your energy, and why, puts you in a much stronger position to have a productive conversation with your doctor about dose timing, alternatives, and solutions.
Antihistamines (Allergy Medications)
First-generation antihistamines like diphenhydramine (Benadryl) and hydroxyzine are among the most reliably sedating medications on the market. They work by crossing the blood-brain barrier and blocking histamine receptors in the central nervous system; since histamine in the brain promotes wakefulness, blocking it effectively puts your alertness into “sleep mode.”
These sedating effects are so powerful that diphenhydramine is the active ingredient in most over-the-counter sleep aids like ZzzQuil and Unisom. Many people take antihistamines daily for hay fever, skin reactions, or vertigo without realizing they are fighting a daily dose of built-in drowsiness. If you use allergy medication regularly and feel foggy or tired, ask your doctor or pharmacist about switching to a second-generation antihistamine like cetirizine or fexofenadine, which are far less likely to cause sedation.
Beta-Blockers (Blood Pressure and Heart Medications)
Beta-blockers like metoprolol (Lopressor), atenolol (Tenormin), and propranolol (Inderal) are workhorses of cardiovascular medicine, but they can leave many people feeling persistently drained. They work by slowing the heart rate and reducing the force of contractions, which is protective for the heart but can cut down on the energy your body feels it has available.
Research shows that up to 30 percent of patients on beta-blockers report fatigue, and a heart rate kept under 60 beats per minute by the medication can deepen that sense of tiredness. Lipophilic beta-blockers like metoprolol and propranolol, which more readily cross into the brain, are more likely than hydrophilic ones to cause central nervous system side effects including fatigue, nightmares, and sleep disturbance.
Mayo Clinic lists “extreme tiredness” as one of the most common beta-blocker side effects. If fatigue is bothering you, your doctor may be able to switch you to a different blood pressure class, such as a calcium channel blocker, which tends to have a less sedating profile.
Benzodiazepines (Anxiety and Sleep Medications)
Benzodiazepines—including alprazolam (Xanax), lorazepam (Ativan), diazepam (Valium), and clonazepam (Klonopin)—are prescribed for anxiety, panic, insomnia, and muscle spasm, and drowsiness, fatigue, and sedation are their most commonly reported side effects. They work by enhancing the activity of GABA, an inhibitory neurotransmitter that damps down activity across the central nervous system.
For older adults, the risks are amplified because it can take up to three times longer to clear these drugs from their bodies, causing the medication to build up and intensify over time.
The American Geriatrics Society’s Beers Criteria identifies benzodiazepines as potentially inappropriate for older adults specifically because of the increased risk of confusion, falls, and daytime sedation. Long-term users may also develop tolerance, requiring higher doses to get the same effect—but with more fatigue as a consequence. If you have been on a benzodiazepine long-term, ask your provider about a slow, medically supervised taper and what alternatives might work for your situation.
Learn more: Read the Beers Criteria summary and benzodiazepine guidance for older adults from NCQA.
Antidepressants
Antidepressants are among the most widely prescribed medications in the country, and fatigue is a common side effect across nearly all classes, though it shows up differently depending on the drug. Tricyclic antidepressants like amitriptyline (Elavil) and doxepin (Silenor) are particularly sedating because they block histamine and acetylcholine receptors in the brain, much like old antihistamines do.
SSRIs like sertraline (Zoloft) and paroxetine (Paxil) tend to cause fatigue most strongly in the first few weeks of treatment, often improving as the body adjusts. Mirtazapine, prescribed for depression and sometimes poor appetite, is notably sedating and is often deliberately given at bedtime.
Antidepressants influence neurotransmitters including histamine, acetylcholine, norepinephrine, and serotonin—all of which play roles in the sleep-wake cycle—making fatigue a predictable risk. Real-world surveys of SSRI users found that sleepiness ranked among the most commonly reported side effects. Switching the dose to bedtime or adjusting which medication you take can often help.
Learn more: A comprehensive review of antidepressant side effects including fatigue is available from PMC.
Anticonvulsants / Nerve-Pain Medications
Drugs used for seizures and nerve pain—including gabapentin (Neurontin), pregabalin (Lyrica), carbamazepine (Tegretol), and topiramate (Topamax)—are well known for causing significant tiredness and mental fog. Gabapentin alone lists somnolence in about 20 percent of clinical trial participants, with fatigue reported in roughly 11 percent.
These medications calm overactive electrical signals in the brain and nervous system, which is helpful for seizures and neuropathic pain but can also quiet the neural activity behind alertness and energy. GoodRx notes that gabapentin can make you feel weaker or like you have less energy than usual, and these effects can persist even after initial adjustment.
Topiramate is sometimes called “Dopamax” by patients because cognitive slowing, tiredness, and word-finding problems are common. If nerve-pain fatigue is disrupting your day, a lower dose, different dosing time, or an alternative within the class may help.
Muscle Relaxants
Muscle relaxants like cyclobenzaprine (Flexeril), baclofen (Lioresal), and carisoprodol (Soma) work primarily in the central nervous system to reduce muscle spasm—but that same CNS-dampening action translates directly into significant daytime fatigue.
Cyclobenzaprine is chemically related to tricyclic antidepressants and research has shown it binds powerfully to histamine H1 receptors in the brain, producing sedation through the same pathway as first-generation antihistamines. Drowsiness was reported by nearly two-thirds of patients taking baclofen in one study.
Muscle relaxants can cause a “hangover effect” that lingers into the next day, particularly in older adults, because the drugs have relatively long half-lives and stay active in the body for extended periods. These medications are listed on the Beers Criteria as potentially inappropriate for older adults because of the risk of sedation, confusion, and falls. When possible, taking them at night rather than during the day can reduce how much daytime function they impair.
Opioid Pain Medications
Prescription opioids—including oxycodone (OxyContin, Percocet), hydrocodone (Vicodin), codeine, and morphine—are powerful pain relievers that also bind to receptors throughout the brain and spinal cord in ways that reliably produce drowsiness, sedation, and clouded thinking.
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The National Institute on Drug Abuse lists drowsiness and confusion among the primary short-term effects of prescription opioids. Memorial Sloan Kettering explains that sedation and clouded thinking can appear within the first day of opioid use or after a dose increase, and for some people these effects never fully go away.
The Rutgers Cancer Institute notes that opioid-induced drowsiness specifically increases the risk of falls, accidents, and injury. Combining opioids with other CNS depressants like benzodiazepines or muscle relaxants compounds the fatigue risk dramatically. If opioid-related tiredness is affecting your quality of life, your prescriber may be able to adjust timing, lower the dose, try a different opioid, or add a short-term stimulant to counteract drowsiness.
Diuretics (“Water Pills”)
Diuretics like furosemide (Lasix), hydrochlorothiazide, and spironolactone are prescribed for high blood pressure, heart failure, and fluid retention, and while they are not traditionally thought of as sedating, they can drain your energy in a roundabout but very real way.
By flushing excess fluid, they also flush out electrolytes—particularly potassium, sodium, and magnesium—and when those minerals drop, fatigue, weakness, and dizziness often follow.
A drop in potassium (hypokalemia), one of the most common side effects of thiazide and loop diuretics, is a well-known cause of muscular weakness and tiredness. Low blood pressure from excess fluid loss is another direct pathway to exhaustion. AARP notes that blood pressure medications including diuretics may “deplete electrolytes that the body needs” and can list “extreme tiredness” in their safety information. Regular blood tests to monitor electrolyte levels are an important part of staying safely and energetically on
Antipsychotic Medications
Antipsychotics—including quetiapine (Seroquel), olanzapine (Zyprexa), haloperidol (Haldol), and risperidone (Risperdal)—are used for schizophrenia, bipolar disorder, and increasingly as augmentation agents for depression or anxiety, and sedation is one of their most predictable effects.
They work partly by blocking dopamine receptors in the brain, and because dopamine plays a key role in motivation, drive, and arousal, this can leave people feeling persistently tired and flat. All antipsychotics can cause sedation, but olanzapine and quetiapine are particularly well known for it.
A recent systematic review confirmed that sedation from antipsychotics has a broadly negative impact on functioning and well-being, affecting a person’s ability to get up in the morning, stay active during the day, and concentrate.
AARP notes that in clinical studies, antipsychotic side effects include “fatigue, lethargy and weakness.” Most antipsychotics can be prescribed as a single bedtime dose to shift the worst sedation to nighttime, which is a practical first step if daytime fatigue is a problem.
Statins (Cholesterol Medications)
Statins—including atorvastatin (Lipitor), simvastatin (Zocor), and rosuvastatin (Crestor)—are among the most widely taken medications in the world, and while they are generally well tolerated, fatigue is a real side effect for a meaningful subset of users.
The UK’s National Health Service lists feeling unusually tired and physically weak as common statin side effects. A landmark randomized controlled trial found that statins had a statistically significant unfavorable effect on energy and exertional fatigue, with effects most pronounced in women taking simvastatin. The likely mechanism is that statins reduce CoQ10 and impair mitochondrial function in muscle cells, reducing the energy supply to muscles and leaving people feeling weak or worn down after physical activity.
Research from Columbia University published in 2025 also found that statins bind to muscle proteins and trigger calcium leaks inside cells, which could explain muscle aches and the fatigue that comes with them. If you are taking a statin and feeling tired, talk to your doctor—switching to a different statin or adjusting your dose often resolves the issue.
Learn more: This is a peer-reviewed study on statins and exertional fatigue from PMC/NIH.
Polypharmacy—When Multiple Medications Stack Their Effects
One medication causing tiredness is manageable. Taking five, six, or eight simultaneously can be a different matter entirely. Polypharmacy—the concurrent use of five or more prescription drugs—affects roughly 39 percent of older adults in the United States, and that number has nearly doubled over the past two decades.
Research published in a national aging survey found that older adults taking three or more medications with somnolence as a listed side effect had a prevalence of excessive sleepiness nearly 20 percentage points higher than those taking none. Drug-drug interactions can amplify the sedating effects of each individual medication, creating a cumulative burden on the brain and body far heavier than any single prescription would cause.
AARP and other organizations note that this “prescribing cascade” can make it genuinely difficult to separate medication fatigue from other causes of tiredness. Bringing a complete, up-to-date medication list—including all over-the-counter drugs and supplements—to every provider appointment is one of the most practical steps you can take to uncover hidden contributors to your exhaustion.
Learn more: Read this peer-reviewed analysis of polypharmacy and somnolence in older adults from PubMed.
Closing Takeaway
Your medication list may be doing far more than treating the conditions printed on the labels—it may also be quietly siphoning your energy every single day. The key is not to stop taking your prescriptions, but to open a direct conversation with your doctor or pharmacist about whether your fatigue could be drug-related.
Small changes—a dose shifted to bedtime, a switch to a less sedating alternative, or a medication review that catches a problematic combination—can sometimes restore energy levels in a matter of days. You deserve to feel as good as the treatment you are getting.
Disclosure: This article was developed with the assistance of AI and was subsequently reviewed, revised, and approved by our editorial team.
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