7 Hydroxychloroquine Side Effects You Should Know About
Key takeaways:
Nausea, vomiting, and diarrhea are the most common side effects of hydroxychloroquine (Plaquenil). Skin rashes are also possible.
Muscle weakness, changes in blood cell counts, and vision changes are rare side effects of hydroxychloroquine. These side effects are more likely to occur with long-term use and higher doses of the medication.
Low blood glucose and heart problems, like QT prolongation, can also occur while taking hydroxychloroquine. But these side effects aren’t common and are more likely to happen if there are other risk factors present.
Table of contents
Like fashion trends, some medications seem to come in and out of style. Hydroxychloroquine (Plaquenil) — originally approved in 1955 as a treatment for malaria — found itself back in the spotlight during the COVID-19 pandemic. Scientists hoped that this medication would turn out to be useful for fighting COVID. But it ultimately fell flat as a treatment for the virus.
Even though hydroxychloroquine isn’t recommended as a treatment for COVID, it’s still an effective treatment for other health conditions, including malaria and certain autoimmune conditions. But there are a few things to know before you start taking it. If you’re prescribed the medication, here are seven of the most common hydroxychloroquine side effects to keep in mind.
1. Nausea, vomiting, and diarrhea
Nausea, vomiting, and diarrhea are the most common side effects of hydroxychloroquine. And some people may also experience stomach pain. Gut-related side effects can happen in up to 37% of people who take hydroxychloroquine.
Nausea related to hydroxychloroquine is often short-lived and can be managed by taking the medication with food. To help reduce nausea, you can also:
Eat smaller, more frequent meals throughout the day.
Try drinking peppermint tea.
Talk to your healthcare provider about whether changing the timing or dose of the medication might help.
Diarrhea related to hydroxychloroquine also tends to improve with time. But, when it occurs, it’s uncomfortable and can lead to more serious conditions, such as dizziness and dehydration. These tips can help calm or treat diarrhea:
Drink plenty of fluids to stay hydrated.
Avoid fatty, fried, and high-fiber foods.
Try an over-the-counter (OTC) antidiarrheal medication, such as loperamide (Imodium A-D), with your healthcare provider’s OK.
2. Skin rashes
Skin rashes are another common hydroxychloroquine side effect. This reportedly affects about 10% of people who take hydroxychloroquine. And it usually occurs within the first 4 weeks of taking the medication.
The most common skin reaction is a red, bumpy, and sometimes itchy rash. It’s often mild and usually goes away after stopping treatment with hydroxychloroquine. More severe skin reactions — such as Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome — can also occur, but they’re much less common. These rare conditions often cause blistering or peeling of the skin, fever, and other body-wide symptoms that are life-threatening.
Hydroxychloroquine can also cause the nails, inside of the mouth, and skin on the arms, legs, and face to turn a blue-gray or black color. This is more likely in people with autoimmune conditions, as they typically take the medication on a long-term basis (for several months or years). Skin discoloration often improves after stopping treatment with hydroxychloroquine, although it rarely goes away completely.
All in all, the type and severity of skin-related side effects from hydroxychloroquine can vary. Let your healthcare team know if you develop a rash at any point while taking hydroxychloroquine. They can check the severity of the reaction and decide if you need to stop taking the medication.
3. Muscle weakness
In rare cases, hydroxychloroquine can cause nerve damage that leads to muscle weakness. While the estimates vary, some studies say that this can occur in up to about 13% of people receiving long-term treatment with hydroxychloroquine. This side effect is more likely with longer use and in people who have kidney issues or who are older. It should go away after stopping treatment with the medication.
Your healthcare provider may periodically monitor your muscle strength and reflexes while you’re taking hydroxychloroquine. Reach out to your healthcare team if you notice weakness that interferes with your daily activities.
4. Low blood glucose
Hydroxychloroquine can also cause low blood glucose (sugar) in rare cases. Common symptoms of low blood glucose include sweating, shakiness, dizziness, and confusion.
If you have diabetes, you’ll want to monitor your blood glucose more closely while taking hydroxychloroquine. This is especially important when you begin treatment and your body is adjusting to the medication.
Let your healthcare team know if you have frequent blood glucose readings below 70 mg/dL. They may want to change the dose of one or more of your diabetes medications to help prevent low readings in the future.
5. Changes in blood cell counts
Hydroxychloroquine intentionally changes how your immune system responds to germs and other types of threats. That’s why it’s used as a treatment for autoimmune conditions: It helps calm an overactive immune response.
However, this can also decrease the amount of important blood cells — including white blood cells, red blood cells, and platelets — in your body. These changes in blood cell counts are rare, but they are more likely with long-term use. Keep these cell types in mind:
White blood cells: These blood cells help fight infection. Let your healthcare team know if you develop any signs or symptoms of infection, such as fever, chills, or muscle aches.
Red blood cells: These blood cells carry oxygen throughout your body and give you energy. Low levels of red blood cells can cause anemia and fatigue.
Platelets: These blood cells help your blood clot when you get a cut or scrape. Your team should know about any unusual bruising or bleeding you develop while you’re taking hydroxychloroquine.
There are also rare scenarios in which hydroxychloroquine causes the body to stop making all three of these important blood cells (aplastic anemia). To help avoid complications from this serious side effect, your healthcare provider will occasionally monitor your blood counts if you’re taking hydroxychloroquine on a long-term basis.
6. Vision changes
Hydroxychloroquine can damage blood vessels in the eye (retinopathy). This can result in decreased or blurry vision — or even vision loss. Thankfully, these side effects are very unlikely with short-term treatment. But larger doses, existing kidney problems, and longer use increase the risk of these side effects.
For example, vision changes affect less than 1% of people who take hydroxychloroquine for 5 years or less. But 20% of people who take the medication for 20 years experience vision changes.
If caught early, vision changes related to hydroxychloroquine can have a minimal impact. In order to monitor for these changes, you’ll likely have an eye exam within the first year of starting treatment with hydroxychloroquine and again after about 5 years. If you have other risk factors for eye problems, your healthcare provider may want you to come in for eye exams every year.
Any vision changes should be reported to your healthcare team immediately. You may have to stop taking hydroxychloroquine if an eye exam shows any damage.
7. Heart problems
Certain heart issues can develop in some people who take hydroxychloroquine. But, again, this is rare.
One of these issues is cardiomyopathy, weakening of the heart that makes it difficult to pump blood around the body. Cardiomyopathy is more likely with higher doses of hydroxychloroquine and in people who take it for a long time. The other main issue is QT prolongation, an abnormal heartbeat that increases the risk for arrhythmias. This can happen with short- or long-term use.
These health conditions and/or medications can increase the risk of these heart problems occuring while taking hydroxychloroquine:
Existing heart conditions or arrhythmias
Abnormal electrolytes, or substances in your blood that keep your body functioning normally
Other medications that affect your heart rhythm, such as antipsychotics and antiarrhythmics
Your healthcare provider may occasionally monitor your heart health while you’re taking hydroxychloroquine by ordering a routine test called an electrocardiogram. This is especially true if you have any additional risk factors.
When should you contact your healthcare provider about hydroxychloroquine side effects?
If you develop side effects at any point while taking hydroxychloroquine, it’s a good rule of thumb to reach out to your healthcare provider. They can offer advice about how to make your symptoms more manageable.
Sometimes, side effects can turn into a more serious problem if left untreated. Reach out to your healthcare provider right away if you develop any of the following symptoms:
Blurry or decreased vision
Chest pain or shortness of breath
Fast or irregular heartbeat
Fever
Lightheadedness
Itchiness or rash (especially blistering of the skin, eyes, lips, or mouth)
Shakiness or sweating
Uncontrolled nausea, vomiting, or diarrhea
Unusual bruising or bleeding
Sudden weakness
New or worsening depression
Good to know: Don’t stop taking hydroxychloroquine without talking to your healthcare team first. If you do, you could experience a flare up in symptoms related to your health condition. Your team will help you decide what the best steps are for managing any side effects that you’re experiencing.
The bottom line
Nausea, diarrhea, and skin rashes are the most common hydroxychloroquine (Plaquenil) side effects. Gut-related side effects are usually manageable, but a rash may require you to stop taking the medication. Decreased blood cell counts, muscle and heart weakness, and vision changes are rare, but they are more likely to occur with higher doses of the medication and longer use.
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References
American Diabetes Association. (n.d.). What is retinopathy?
Bansal, P., et al. (2021). Hydroxychloroquine: A comprehensive review and its controversial role in coronavirus disease 2019. Annals of Medicine.
Bryant Ranch Prepack. (2023). Hydroxychloroquine sulfate [label]. DailyMed.
Coulombe, J., et al. (2017). Hydroxychloroquine-related skin discoloration. Canadian Medical Association Journal.
Fairley, J. L, et al. (2022). How toxic is an old friend? A review of the safety of hydroxychloroquine in clinical practice. International Medicine Journal.
Gisondi, P., et al. (2021). The safety profile of hydroxychloroquine: Major cutaneous and extracutaneous adverse events. Clinical and Experimental Rheumatology.
Labib, A.M., et al. (2022). Toxic epidermal necrolysis. StatPearls.
Marmor, M. F., et al. (2016). Recommendations on screening for chloroquine and hydroxychloroquine retinopathy (2016 revision). American Academy of Ophthalmology Statement.
National Heart, Lung, and Blood Institute. (2022). Aplastic anemia.
U.S. Food & Drug Administration (n.d.). Drugs@FDA: FDA-approved drugs. New drug application (NDA): 009768.
U.S. Food & Drug Administration. (2020). Coronavirus (COVID-19) update: FDA revokes emergency use authorization for chloroquine and hydroxychloroquine.
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