Chondroitin has been taken safely in oral doses of up to 2000 mg /day for up to six years. In most studies similar rates and types of adverse effects have been seen for chondroitin and placebo, but few studies have run for longer than two years.
Most often, the adverse effects that occur with chondroitin are gastrointestinal and non-serious. However, skin reactions and respiratory effects have also been reported. Since there have been reports of liver injury, it may be best for anyone with chronic liver disease to avoid chondroitin.
Of the adverse reactions reported to the UK Medicines and Healthcare Products Regulatory Authority (MHRA) for chondroitin sulphate (alone, not in combination with glucosamine), the most common (around 30%) were gastrointestinal disorders, and included nausea, vomiting, bloating, abdominal pain and diarrhoea.
Since the amount of chondroitin that is absorbed form the gut may be as low as 12%, some of these gastrointestinal effects may be the result of its local action on the gut.
Taking chondroitin with or after food may help with some of these symptoms.
The UK MHRA has received reports of adverse liver effects with chondroitin sulphate. There are also published reports of liver effects in people taking chondroitin preparations with and without glucosamine. In one case, liver injury that mimicked autoimmune hepatitis was associated with a combined chondroitin and glucosamine preparation. In another, auto-immune hepatitis was reported in a 64-year old woman one month after starting oral chondroitin (without glucosamine) for osteoarthritis. The woman’s liver function normalised four months after discontinuing the supplement. Chondroitin may not be suitable for people with chronic liver disease.
Caution is recommended with the use of chondroitin in patients with asthma. A 52-year-old woman with a 10-year history of intermittent asthma who started to take a combined glucosamine and chondroitin preparation experienced worsening of her asthma. Inhaled and oral steroids had no lasting beneficial effect on the patient’s symptoms, which disappeared within 24 hours of discontinuing the preparation. The cause of the asthma exacerbation was not determined.
Adverse skin reactions with chondroitin reported to the UK MHRA constituted about 10% of all the reported reactions for chondroitin, and included rash, purpura and photosensitivity. There are published reports of swollen eyelid, swollen leg and alopecia in patients taking chondroitin orally.
Chondroitin is a component of the anticoagulant danaparoid so could be expected to have blood thinning effects. In practice, there is little evidence of it causing bleeding problems in people who take it orally. However caution is recommended in anyone taking chondroitin who has a known increased risk of bleeding.