Glucosamine + Chondroitin

What it is

Glucosamine and chondroitin are building blocks of cartilage and joint fluid, supplied as an over-the-counter supplement on the premise of supporting the cartilage matrix. The combination is taken for joint complaints, most often knee osteoarthritis. Any benefit is modest and gradual rather than immediate.

Used for

• Joints

What to know while taking it

It is taken with food, and it works slowly: weeks pass before any change is noticeable, so it is judged over a course rather than day to day. Glucosamine is usually manufactured from shellfish shells, which matters for anyone with a shellfish allergy. It can potentiate warfarin and raise INR, so combining the two needs the prescriber's knowledge and closer monitoring. Blood glucose is worth keeping an eye on, particularly in diabetes, as glucosamine is an amino sugar.

When to see a doctor

Bleeding or bruising on warfarin, an allergic reaction such as rash, swelling or breathing difficulty, or glucose readings that climb out of the usual range all mean seeing a doctor. Joint pain that keeps worsening, swells or locks the joint needs proper assessment rather than a longer supplement course.

Worth knowing

• Takes weeks to work
• Often derived from shellfish

Markers to watch

• Glucose