Safety and side effects

When taken in appropriate amounts, glucosamine sulfate appears to be safe. Oral use of glucosamine sulfate can cause:

• Nausea
• Heartburn
• Diarrhea
• Constipation

Other side effects may include:

• Drowsiness
• Skin reactions
• Headache

Because glucosamine products might be derived from the shells of shellfish, there is concern that the supplement could cause an allergic reaction in people with shellfish allergies.

Glucosamine might worsen asthma.

There's some concern that glucosamine might raise eye pressure. If you have glaucoma, talk to your doctor before taking glucosamine supplements.