High Doses of the Vitamin B3 Supplement Nicotinamide for Glaucoma May Cause Liver Damage

Glaucoma refers to a group of chronic eye diseases that can damage the optic nerve, leading to vision loss and blindness without prompt treatment.[1],[2] Although early signs and symptoms are often not noticeable, they can be detected through regular comprehensive eye exams by an optometrist or ophthalmologist.

A major risk factor for glaucoma is an increase in pressure within the eye, known as intraocular pressure. Unfortunately, even when increased intraocular pressure is successfully treated with medications, many patients with glaucoma continue to have optic nerve damage and visual-field loss.

Recently, supplementation with nicotinamide, a form of vitamin B3, has been tested as an additional way to protect the optic nerve in patients with glaucoma. Although studies are ongoing, nicotinamide is not approved to treat glaucoma and its safety is unknown.

This article discusses a January 2025 position paper from the American Glaucoma Society and the American Academy of Ophthalmology about the use of nicotinamide for glaucoma and the risk of drug-induced liver damage.[3] Because nicotinamide is a dietary supplement, it can be obtained without a prescription.

If you have glaucoma, Public Citizen’s Health Research Group agrees with the position paper and recommends that you do not use high-dose nicotinamide unless you are enrolled in a clinical trial where your liver function is closely monitored. If you have liver disease or have had liver disease in the past, you should not use nicotinamide supplements at all.

Niacin — another dietary supplement — is also a form of vitamin B3. Niacin and nicotinamide, however, are not interchangeable. Niacin is known to damage the liver in high doses and is not being tested as a glaucoma treatment.[4]

Background on glaucoma

About 3 million people in the United States have glaucoma.[5] Although it can affect anyone, the eye disease is most common in those with a family history of glaucoma and adults older than 60 years. Moreover, Black individuals older than 40 are six to eight times more likely than White individuals to develop glaucoma. Additionally, people with diabetes are twice as likely as those without diabetes to develop glaucoma.

The exact causes of glaucoma are not known and there is currently no cure.[6] The most common treatment is to relieve high eye pressure with prescription eye drops.[7] If eye drops do not work sufficiently, oral medicine, laser treatment, or more intensive surgery to help drain fluid from eyes can become necessary.

Nicotinamide entered the picture recently, after findings from studies in animals and people suggested that high-dose supplementation can help protect the optic nerve in patients with glaucoma.[8]

Background on vitamin B3

Vitamin B3, both in the form of nicotinamide and of niacin, can be found in many multivitamin supplements and helps the body turn food into a source of energy.[9] Vitamin B3 also is important for cell function. Most people get enough vitamin B3 from the food they eat.

Especially at high doses, niacin supplementation is associated with liver disease, including liver failure. Supplementation with nicotinamide is associated with fewer adverse events, but at high doses (500 milligrams [mg]/day or greater) it can cause diarrhea, easy bruising, or bleeding. At even higher doses (3,000 mg/day), nicotinamide use can lead to vomiting, nausea and liver damage.

The clinical trials assessing the effect of nicotinamide on glaucoma used supplementation with about 3,000 mg of nicotinamide daily, which is 150 times the recommended daily dose of 20 mg a day.[10] To protect participants from drug-induced liver injuries, all trials excluded patients with a history of liver disease. Despite this, among the more than 300 participants in completed and ongoing glaucoma studies, at least two cases of drug-induced liver injury have been identified.

Moreover, the available results have not established either the safety of nicotinamide supplementation or whether the supplement can slow the progression of glaucoma in the long term.[11],[12] The position paper cautioned that the potential benefit of nicotinamide may only be “detectable in a research setting” and may not lead to “visual recovery that is impactful to the patient.”[13]

For this reason, these medical groups caution that high-dose nicotinamide for glaucoma treatment should only be considered as part of a clinical trial where liver function is closely monitored. When lower doses are being considered, which Public Citizen’s Health Research Group does not recommend outside of a clinical trial, this should only be done in collaboration with a primary care physician and with periodic liver-function testing.

What You Can Do

Do not take nicotinamide or niacin supplements to prevent or treat glaucoma unless you are enrolled in a clinical trial. If you develop possible adverse effects of nicotinamide, such as bloating, constipation, nausea or headache, report them immediately to study investigators or your primary care physician so that they can be evaluated. Seek immediate care if you develop signs of drug-induced liver injury, such as jaundice (yellowing of the skin or eyes), dark urine or light-colored stools.

Make sure to get regular comprehensive eye exams, especially if you are at a higher risk of developing glaucoma or other eye diseases. If you develop new visual symptoms, such as blind spots in your peripheral vision, promptly consult with an eye clinician. Healthy lifestyle habits such as being physically active, maintaining a healthy weight, and keeping blood pressure under control can help to prevent vision loss from glaucoma.
 

References

[1] Shukla AG, Cioffi GA, John SWM, et al. American Glaucoma Society-American Academy of Ophthalmology position statement on nicotinamide use for glaucoma neuroprotection. Ophthalmol Glaucoma. 2025 Jan 10:S2589-4196(25)00007-9.

[2] National Eye Institute. Glaucoma. December 10, 2024. https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/glaucoma. Accessed March 5, 2025.

[3] Shukla AG, Cioffi GA, John SWM, et al. American Glaucoma Society-American Academy of Ophthalmology position statement on nicotinamide use for glaucoma neuroprotection. Ophthalmol Glaucoma. 2025 Jan 10:S2589-4196(25)00007-9.

[4] National Institutes of Health. Niacin: Fact sheet for consumers. March 21, 2022. https://ods.od.nih.gov/factsheets/Niacin-Consumer/. Accessed March 11, 2025.

[5] Centers for Disease Control and Prevention. About glaucoma. May 15, 2024. https://www.cdc.gov/vision-health/about-eye-disorders/glaucoma.html. Accessed March 10, 2025.

[6] National Eye Institute. Glaucoma. December 10, 2024. https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/glaucoma. Accessed March 10, 2025.

[7] National Eye Institute. Glaucoma medicines. December 5, 2024. https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/glaucoma/glaucoma-medicines. Accessed March 10, 2025.

[8] Shukla AG, Cioffi GA, John SWM, et al. American Glaucoma Society-American Academy of Ophthalmology position statement on nicotinamide use for glaucoma neuroprotection. Ophthalmol Glaucoma. 2025 Jan 10:S2589-4196(25)00007-9.

[9] National Institutes of Health. Niacin: Fact sheet for consumers. March 21, 2022. https://ods.od.nih.gov/factsheets/Niacin-Consumer/. Accessed March 11, 2025.

[10] Shukla AG, Cioffi GA, John SWM, et al. American Glaucoma Society-American Academy of Ophthalmology position statement on nicotinamide use for glaucoma neuroprotection. Ophthalmol Glaucoma. 2025 Jan 10:S2589-4196(25)00007-9.

[11] De Moraes CG, John SWM, Williams PA, et al. Nicotinamide and pyruvate for neuroenhancement in open-angle glaucoma: A phase 2 randomized clinical Trial. JAMA Ophthalmol. 2022 Jan 1;140(1):11-18.

[12] Hui F, Tang J, Williams PA, et al. Improvement in inner retinal function in glaucoma with nicotinamide (vitamin B3) supplementation: A crossover randomized clinical trial. Clin Exp Ophthalmol. 2020 Sep;48(7):903-914.

[13] Shukla AG, Cioffi GA, John SWM, et al. American Glaucoma Society-American Academy of Ophthalmology position statement on nicotinamide use for glaucoma neuroprotection. Ophthalmol Glaucoma. 2025 Jan 10:S2589-4196(25)00007-9.