Niacin, also known as vitamin B3, is often taken to lower cholesterol and manage high levels of fat in the blood. While it can help, using too much niacin without a doctor’s advice can lead to serious problems—including damage to your eyes.
A new study from the New York Eye and Ear Infirmary of Mount Sinai highlights the risks of taking high doses of niacin without medical supervision. One patient in the study nearly went blind after months of taking large amounts of the vitamin on his own.
The patient was a 61-year-old man who had been taking between 3 to 6 grams of niacin every day for several months. He hoped the supplement would protect his heart. However, he did not tell his doctors about his supplement use at first. He only mentioned that he had high blood pressure and cholesterol.
Over time, his eyesight became worse and worse. When he arrived at the hospital, his vision was so poor he could barely read the largest letters on an eye chart. One eye was 20/150 and the other 20/100—close to being legally blind.
Doctors later discovered the cause: he had been taking too much niacin. The usual dose for treating high cholesterol is between 1 and 3 grams per day. Six grams is considered the maximum, and even that should only be taken with a doctor’s close supervision. The man had been self-medicating with over-the-counter niacin, not knowing the risks.
Using special imaging tools, doctors found he had a rare eye problem called niacin-induced cystoid maculopathy. This condition causes swelling in the macula, the part of the eye that lets us see fine details. The swelling happens because too much niacin causes fluid to build up in the retina, making vision blurry.
Thankfully, his condition was caught early and was reversible. Doctors told him to stop taking niacin right away. Just one week later, his eyesight began to improve. Two months later, the swelling was gone and his vision was fully back to normal—20/20 in both eyes.
This case is a strong warning. Just because you can buy a vitamin at the store doesn’t mean it’s completely safe to take in high doses. Some supplements can be dangerous if taken without medical advice. In this case, too much niacin nearly caused permanent vision loss.
The lesson is clear: always talk to your doctor before starting any high-dose supplement. If you ever notice changes in your vision, don’t wait—get medical help right away.
The study was led by Dr. Richard Rosen and published in the Journal of VitreoRetinal Diseases. It shows how important it is to use vitamins and supplements responsibly and with medical guidance.
If you care about eye health, please read studies about how vitamin B may help fight vision loss, and MIND diet may reduce risk of vision loss disease.
For more information about eye disease, please see recent studies about how to protect your eyes from glaucoma, and results showing this eye surgery may reduce dementia risk.
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