From Chest Pain to Vision Changes: 10 Medication Side Effects You Should Never Ignore

Medications are designed to help us heal, alleviate symptoms, and lower our risk of serious health problems. However, they can also come with a range of side effects. In many cases, these side effects are perfectly normal and harmless.

And yet, there are certain medication side effects that should never be brushed aside. In some cases, recognizing and addressing these symptoms promptly can be a matter of life and death.

Below are 10 medication side effects you should always take seriously. Keep in mind that this list doesn’t include all potentially serious side effects.

1. Severe allergic reactions

While rare, some people experience a severe allergic reaction (anaphylaxis) after taking a medication. This may be due to the active ingredient, such as with penicillin or sulfa antibiotics. But it can also be from an inactive ingredient in the medication, such as artificial dyes. That’s why it’s important to give your healthcare provider and pharmacist a list of your allergies to review in advance.

Anaphylaxis symptoms usually start shortly after taking the medication. But they can also develop a few hours later. Symptoms of anaphylaxis include:

• Red or itchy skin

• Hives

• Tightness in the throat

• Swelling of the face, lips, or tongue

• Chest tightness or difficulty breathing

• Abdominal pain

• Vomiting or diarrhea

• Racing heart beat

• Lightheadedness 

This type of reaction can progress quickly and become life-threatening if left untreated. If you think you’re having a severe allergic reaction to a medication, don’t wait it out. Use injectable epinephrine (such as an EpiPen) if it’s available and call 911 right away. 

2. Chest pain

Chest pain doesn’t always mean you’re having a heart attack. But it’s not something you should ignore. And if you’re taking certain medications, chest pain that’s not going away may be more concerning.

While uncommon, some medications can increase the risk of a heart attack. And if you have a pre-existing heart condition or other risk factors, they may be used with caution or avoided altogether. Examples of these medications include:

• Nonsteroidal anti-inflammatory drugs (NSAIDs)

• Triptans such as sumatriptan (Imitrex)

• Stimulant medications such as Adderall

• Hormonal birth control (especially higher estrogen doses)

If you are experiencing chest pain — especially pain that’s severe, won’t go away, or is getting worse — go to the nearest emergency room to get checked out. But even if the pain doesn’t feel severe, a trip to the emergency room is still a good idea. Especially if it’s chest pain that you’ve never had before. 

Good to know: Certain medications, like triptans, can cause temporary chest pain or tightness after taking them. This isn’t usually a cause for concern in most cases. But rarely, heart attacks have occurred in some people taking them.

3. Irregular heartbeat

Some medications can lengthen the time it takes your heart to reset between beats. This is called QT prolongation (or long QT syndrome). QT prolongation can increase the risk of potentially life-threatening heart rhythm problems.

QT prolongation doesn’t always cause noticeable symptoms. In this case, your healthcare provider might find it during a routine checkup. But you should get medical attention right away if you are having a racing, skipping, or fluttering heartbeat. And if you feel like you’re about to faint, call 911 immediately. This could be a sign of a more dangerous heart rhythm. 

There are many medications that can cause QT prolongation to varying degrees. Examples include:

• Heart rhythm medications such as amiodarone

• Antibiotics such as ciprofloxacin and erythromycin

• Antidepressants such as citalopram (Celexa)

• Antihistamines such as diphenhydramine (Benadryl)

Taking higher doses of these medications may increase the risk of QT prolongation. So it’s important to take them as directed. Drug interactions can also make this side effect more likely. Make sure your current medication list is up to date so your healthcare team can screen for concerning interactions ahead of time.

4. Bleeding

If you’re taking a blood thinner to treat or prevent blood clots, bleeding is a common side effect. Examples of blood thinners include:

• Warfarin

• Apixaban (Eliquis)

• Rivaroxaban (Xarelto)

• Aspirin

• Clopidogrel (Plavix)

When taking these medications, you may notice minor bleeding, such as increased bruising or bleeding gums. This isn’t necessarily serious, but it’s still a good idea to let your healthcare provider know. 

But more serious bleeding is also possible and requires immediate medical attention. This includes:

• Nosebleeds, especially if they’re hard to stop

• Bloody or black stools

• Blood in your urine

• A severe headache

• Bruising that covers a large part of your body

While less common, there are other medications that can also increase the risk of bleeding. Bleeding may be more likely if you’re taking more than one, or if you combine them with blood thinners. Examples include:

• NSAIDs such as ibuprofen (Advil, Motrin)

• Selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine (Prozac)

• Serotonin and norepinephrine reuptake inhibitors (SNRIs) such as venlafaxine (Effexor)

5. Seizures

Some medications can increase the risk of having a seizure — even if you’ve never had one before. This is because they can lower the seizure threshold, which is how likely you are to have a seizure. Examples of these medications include:

• Bupropion (Wellbutrin)

• Antipsychotic medications such as clozapine (Clozaril)

• Cyclobenzaprine

• Diphenhydramine

• Tramadol

Higher doses of these medications are more likely to cause seizures. So, it’s important to take them as prescribed. Certain drug interactions can also raise the seizure risk. Make sure your healthcare provider and pharmacist are aware of other medications you take. Anytime anyone has a seizure for the first time, it’s best to call 911.

Good to know: Seizures can also be a severe symptom of serotonin syndrome, which can be caused by medications that affect serotonin, such as SSRIs. They can also happen if you stop certain medications too quickly, such as benzodiazepines and baclofen. Serotonin syndrome is life-threatening and also requires emergency care.

6. Severe nausea, vomiting, and stomach pain

Many medications can cause nausea, vomiting, stomach pain, and other gastrointestinal (GI) side effects. While unpleasant, these side effects are often mild and improve over time.

But sometimes GI side effects can become severe. And while rare, this can sometimes indicate a more serious problem from the medication, such as inflammation of the pancreas or gallbladder. A few examples of this includes:

• Pancreas or gallbladder problems from medications like semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro)

• Ovarian hyperstimulation from fertility medications like clomiphene (Clomid)

• Peptic ulcers from NSAIDs

• Toxicity from methotrexate (more likely with higher doses used to treat cancer)

Severe stomach pain that’s getting worse or won’t go away warrants a trip to the emergency room. Jaundice (yellowing of the skin and eyes) can be a sign of pancreas or gallbladder problems that also requires immediate medical attention — even if you don’t have any other GI symptoms.

7. Mental status changes

Mental status changes are another medication side effect that shouldn’t be overlooked. Sudden confusion, hallucinations, and trouble thinking or remembering things are a few examples. Agitation and aggression are also possible with certain medications.

A few examples of these include:

• Sudden confusion (delirium) in older adults from taking sedatives and other risky medications

• Hallucinations and delirium from beta blockers and sleep medications

• Slowed thinking or confusion from medications such as diphenhydramine, amitriptyline and oxybutynin

• Agitation, hallucinations, and confusion from medications such as montelukast (Singular), clonazepam (Klonopin), and levetiracetam (Keppra).

Mental status changes from medications usually aren’t common. But they may be more likely to happen in older adults. And since mental status changes can have several different causes, including medications, it’s important to address them right away.

8. Rash or skin changes

There are several different types of skin reactions that can happen after taking a medication. While rare, severe, life-threatening reactions are possible. These can include Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS).

There are many medications linked to serious skin reactions. Common examples include:

• Seizure medications such as lamotrigine (Lamictal) and carbamazepine (Tegretol)

• Sulfasalazine (Azulfidine)

• Antibiotics such as sulfamethoxazole / trimethoprim (Bactrim)

• NSAIDs

These reactions often involve a rash with other body-wide symptoms, such as fever. And they can develop a few weeks after starting — or sometimes stopping — a medication. If you notice a new rash along with other new symptoms after starting a new medication, seek emergency medical care.

9. Difficulty breathing or shortness of breath

While rare, some medications can harm your lungs.This is due to scarring in the lungs that leads to stiffness, which can make it more difficult to breathe. Other medications can cause inflammation in the lungs. Examples of these include:

• Chemotherapy such as bleomycin and gemcitabine

• Immunotherapy medications such as pembrolizumab (Keytruda)

• Amiodarone

• Leflunomide

• Methotrexate

Some medications can cause or worsen heart failure. Shortness of breath, along with swelling and fatigue are symptoms to look out for. Examples of these medications include:

• NSAIDs

• Thiazolidinediones (TZDs) such as pioglitazone

• Dipeptidyl peptidase-4 (DPP-4) inhibitors such as sitagliptin (Januvia)

• Calcium channel blockers that affect heart rate, such as diltiazem

If you’re taking one of these medications, your healthcare provider may want to monitor your lungs or heart more closely. But you should let them know right away if you develop symptoms such as shortness of breath.

10. Vision changes

Some medications can affect your vision. This can include sudden vision loss, double vision, or any other unusual visual symptoms. And sometimes these vision changes can be a sign of a more serious condition beyond those only affecting your eyes.

Examples of concerning vision changes that can happen from medications include:

• Vision loss in one or both eyes like taking medications like sildenafil (Viagra) or amiodarone (Pacerone)

• Cloudy or blurred vision, seeing halos around lights, or difficulty seeing at night while taking tamoxifen (Soltamox)

Sudden vision changes can sometimes be associated with increased pressure in the brain. Headache, nausea, and vomiting are also common symptoms. While rare, this can be caused by certain medications, including:

• Isotretinoin (Accutane)

• Tetracycline antibiotics

• Lithium

If you notice new vision changes along with a new headache, this could be a medical emergency. It’s best to call 911.

But any of the above vision changes can still be serious. So it’s important to let your healthcare provider know right away if these symptoms develop and to keep up with your regular eye exams.

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Written by:

Alyssa Billingsley, PharmD

Alyssa Billingsley, PharmD, is the director of pharmacy content for GoodRx. She has over a decade of experience as a pharmacist and has worked in clinical, academic, and administrative roles.

Reviewed by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

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