HCQ is generally well tolerated. Rare side effects associated with HCQ include upset stomach, diarrhea, headaches and dizziness. HCQ can also cause a rash, darkening of the skin and ringing in the ears. If you develop a rash or ringing in the ears while on HCQ, please contact your health-care provider.
HCQ can sometimes make your skin more sensitive to the sun, meaning you may sunburn more easily.
In rare cases, HCQ can cause problems with your vision and with the back of the eye (retina). The most common vision-related issue are corneal deposits. This is usually due to high daily doses or HCQ and rarely occurs at doses of 400 mg per day or less. The deposits do not affect vision but can cause sensitivity to light and the appearance of halos or rings around lights. Very rarely HCQ can cause deposits at the back of the eye (retinal deposits). If this occurs, you might notice blurred vision, decreased night and peripheral vision, difficulties focusing your eyes, reading or seeing words and letters, and parts of objects may also appear to be missing. Damage to the retina is extremely rare in cases where a person has been taking HCQ for less than two years. However, once damage occurs, it may be permanent, therefore, appropriate monitoring of your eyes is essential.