Glucosamine might increase eye pressure

Q. I stopped glucosamine when I found that it can increase eye pressure in glaucoma. My cholesterol on my next checkup a year later was 150. I always was around 210 before then. Now I wonder if the fortunate drop was due to stopping glucosamine.

A. There is very little published research linking glucosamine to elevated cholesterol levels. That said, we have received many reports from readers like you. Arthur wrote: “I have a high cholesterol reading (249) since taking glucosamine and chondroitin for osteoarthritis in both my knees. I am careful what I eat and exercise religiously.”

When it comes to glaucoma, there is evidence that glucosamine can increase intraocular pressure (Journal of Glaucoma, April 1, 2024). The authors urge ophthalmologists to ask patients about glucosamine use and discourage this supplement if eye pressure is elevated.

Q. I’m a retired nurse. Back in January 2022, I started on 500 mg of berberine twice a day. My HbA1c had been above 8 for almost five years although I was on insulin. In March 2022, I dropped to 7.4, then to 6.7 in July 2022. I have never been below 7 before in the 25 years I’ve been a diabetic.

I feel fantastic now. I am doing everything I can to get the word out about this supplement.

I ran this by my doctor when she was looking at the graph of my A1c results. She said it looked like my levels were about the same until suddenly they dropped as the berberine kicked in. It does take some time to work well.

I am off insulin now under medical supervision. My cousin, who was a brittle diabetic, is now down to A1c of 5.1 after 18 months on berberine.

A. HbA1c is a test of blood sugar over a span of two to three months. It provides a better overview of type 2 diabetes than individual blood glucose readings. Diabetes is diagnosed when A1c levels are over 6.4.

Berberine has a number of intriguing actions. It has been shown to improve blood sugar control (Frontiers in Pharmacology, July 16, 2025). Other potential benefits of berberine include lowering cholesterol and reducing inflammation. This natural compound may also have an anticancer effect (Metabolism Open, Sept. 25, 2025).

To learn more about many ways to manage blood sugar, you may wish to read our eGuide to Preventing and Treating Diabetes. This online resource can be found under the Health eGuides tab at www.PeoplesPharmacy.com.

Some people taking berberine complain about digestive difficulties. Anyone taking berberine should check with a pharmacist since this botanical supplement may interact with a number of medications.

Q. I spent at least half my life plagued with sinus infections until I heard about xylitol. I had been using irrigation for many years, and it helped. But when I began adding a small amount of xylitol to my bottle of nasal wash, the sinus problems became a part of my past. It felt like a miracle!

Also, xylitol is cheap. One important warning for pet owners, however, is that it is detrimental to pets.

A. Thanks for the testimonial. Xylitol, a natural antibacterial agent, is beneficial and safe as part of nasal irrigation (Biomedicines, June 20, 2024).

Xylitol is available in OTC nasal spray and sinus rinse under the brand name Xlear. If you make your own rinse for irrigation, be sure to use sterile water for safety.

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In their column, Joe and Teresa Graedon answer letters from readers. Write to them in care of this newspaper or e-mail them via their Web site: www.PeoplesPharmacy.com. Their newest book is Top Screwups Doctors Make and How to Avoid Them (Crown)

This story was originally published October 29, 2025 at 6:00 AM with the headline "Glucosamine might increase eye pressure."