Glucosamine Chondroitin For Knee Pain: Side Effects | 5 Complications + How To Avoid Them

Written By on March 27, 2022 — Medically Reviewed By Mich Torres

Written by on March 27, 2022 — Medically Reviewed By: Mich Torres

One of the most widely used dietary supplements is glucosamine chondroitin for knee pain. Side effects are rare, though – usually mild gastrointestinal discomfort.

But, people with certain conditions may have more severe side effects. Like an allergic reaction or increased blood sugar, to name a few.

Below, we’ll discuss the 5 most common side effects of taking glucosamine sulfate supplements and how to avoid them.

Here are the topics we’ll cover, tap on any of the topics to navigate through the article:

5 potential side effects of glucosamine and chondroitin sulfate

Person grabbing their stomach in pain due to a side effect of glucosamine chondroitin for their knee pain

1) Can cause stomach issues

Taking glucosamine chondroitin can cause an upset stomach in some people. This may present as nausea, vomiting, constipation, diarrhea, heartburn, or other stomach-related issues. 

Studies have shown that it’s safe to take a daily dosage of 1500mg of glucosamine sulfate and 800 mg of chondroitin sulfate. At least for up to 12 weeks and in healthy adults. (1)

Taking supplements as per this recommendation can also reduce the risk of stomach issues. 

Also, this side effect can be more pronounced if you take glucosamine chondroitin with painkillers. Please avoid taking them in combination.

Finally, one way to prevent stomach upset is to consume the supplements with food rather than on an empty stomach. 

Learn more: Safe dosage of glucosamine for knee pain

2) Can cause an allergic reaction in people with shellfish allergies

Supplements of glucosamine are mostly derived from crabs and shellfish. If you are allergic to these, be cautious before taking these supplements.

Knee Force Knee Sleeve

If you have seafood allergies and accidentally consume glucosamine supplements, you’ll probably have an allergic reaction.

The symptoms can range from mild to severe, including:

  • Itching.
  • Swelling of the mouth or face.
  • Rashes.
  • Difficulty breathing.

Most of the allergic reactions are mild and subside easily. But if you have them, please stop taking glucosamine supplements made from shellfish and consult your physician.

Pro tip: Look for plant-derived forms of glucosamine – these are safe for those with shellfish allergies.

3) May affect blood sugar levels for diabetic patients

Studies have shown that glucosamine chondroitin can raise blood glucose levels. This can be a big challenge for people with diabetes. (2)

See – in healthy people, insulin works properly and it’s able to keep our sugar levels within a healthy range.

But glucosamine chondroitin can affect the way insulin works. So, there’s a risk of glucose accumulating in the bloodstream. (2)

Now, in diabetes, the insulin level is already low or it isn’t working as it should.

So, glucosamine chondroitin can interfere with insulin even more.

However, some studies suggest that taking 1200 mg of glucosamine per day may not increase blood glucose in people with diabetes. (2, 3)

This is a little less than the normal dose of glucosamine chondroitin – 1500 mg per day.

However, if you’re diabetic, consult with your physician first before taking these supplements.

You should have your blood sugar checked before supplementing with glucosamine chondroitin. Your doctor may need to adjust your medications, too.

This is crucial if you’re already on multiple anti-diabetic drugs.

4) Can make you bleed easier if you’re on anticoagulants

If you are on anticoagulant medications, then please consult your physician before starting to take glucosamine and chondroitin supplements.

See, these supplements can interact with certain anticoagulant medications – like warfarin. (4, 5) But you can keep this at bay by doing a PT/INR test, which monitors the effect of anticoagulants in your blood.

This test can help your doctor evaluate the interaction between glucosamine and anticoagulants. So, an increase in PT/INR suggests an increased effect of anticoagulants.

Hence, an increased risk for side effects, like spontaneous bleeding. 

Signs to watch out for while taking glucosamine and anticoagulants:

  • Blood around your gums or your toothbrush after brushing your teeth.
  • Sudden or easy bruising.
  • Spontaneous nosebleed.
  • Increased blood flow during menstruation.

If you have any of the above after starting on glucosamine sulfate and chondroitin, please stop taking the supplements and make an appointment with your doctor.

5) Some ingredients aren’t suitable for vegans/vegetarians

Although not a side effect, vegetarians and vegans may want to double-check the ingredients before purchasing glucosamine supplements.

As mentioned above, glucosamine chondroitin is most commonly derived from animal sources. Primarily shellfish, crabs, and other crustaceans.

Luckily, there are plant-based forms of glucosamine chondroitin.

However, there are no studies yet showing the effectiveness of plant vs animal-based glucosamine chondroitin supplements.

Knee Force Knee Sleeve

Theoretically, the effects should be similar regardless of the source.

Safe doses of glucosamine chondroitin: Can you overdose?

Man with half of his face with yellowed skin and eyes, a sign of liver damage, and the other side of the face normal

The safe daily dose of glucosamine is 1500 mg, while for chondroitin is 1200 mg. This is either in single or divided amounts. (5)

Sticking to those quantities can provide joint pain relief, lessen osteoarthritis pain, and help other knee symptoms without significant side effects.

However, keep in mind that taking much higher quantities won’t provide more benefits.

In fact, taking glucosamine chondroitin at extremely high doses can result in overdose and toxicity. This is extremely hard to pull off, but the consequences are severe.

Can you overdose on glucosamine chondroitin supplements?

Clinical trials on animals have shown that the lethal dose of glucosamine is around 8000 mg per kg body weight. However, no adverse effects were seen in up to 2700 mg per kg body weight. (6)

Following this data, an average healthy adult would have to take more than 350 pills of the supplement for a lethal dose of glucosamine.

And although extremely rare, a glucosamine overdose will cause liver problems.

If you accidentally or intentionally consume large doses of glucosamine, you can suffer from a drug-induced liver injury. You would notice it due to the following symptoms:

  • Yellowing of the eyes and skin.
  • Having dark yellow urine.
  • Pain in the abdomen.

If you’re experiencing any of those symptoms, please go immediately to the emergency room.

In these cases, the patient might be treated in the emergency room aggressively. This might be seen in people who ingest large amounts accidentally or with a tendency to cause self-harm.

Depending on the severity of the damage, people with glucosamine overdose may need to stay in the hospital until their liver heal.

Which form of glucosamine is the safest?

Both sulfated and hydrochloride forms of glucosamine are safe. 

The recommended dose of either hydrochloride or sulfate form is 1500 mg per day. You can take it in a single or divided dose of 500 mg three times per day. (7

However, it’s worth noting that the hydrochloride form contains greater amounts of glucosamine than its sulfated counterpart. So, you may have more glucosamine available when taken in hydrochloride form. (7)

You may need professional medical advice to know which form will suit you best. More so if you have a previous medical condition.


Can glucosamine sulfate cause liver damage?

Extremely large amounts of glucosamine can cause liver damage.

Do glucosamine and chondroitin have side effects? 

Yes, glucosamine and chondroitin have side effects but most are minor – nausea, vomiting, or diarrhea. 

Can you overdose on glucosamine and chondroitin supplements?

Yes, accidental or intentional intake of extremely large amounts of glucosamine chondroitin can cause you to overdose. However, this is extremely hard to do.

Is it safe to take glucosamine chondroitin sulfate daily?

Yes, it is safe to use 1500mg of glucosamine and 1200mg of chondroitin daily. (6)

Conclusion: Risks of glucosamine chondroitin for osteoarthritis pain

Although glucosamine chondroitin is safe for managing knee pain, some people may suffer from mild side effects, such as:

Stomach upset, rise in blood glucose, an increased risk of bleeding, or allergic reactions. Please visit your doctor if you suffer from any of them to check what’s going on.

Finally, this advice applies to knee pain in general, whether it’s due to rheumatoid arthritis, knee osteoarthritis, or other conditions.


  1. Vasiliadis, Haris S, and Konstantinos Tsikopoulos. “Glucosamine and chondroitin for the treatment of osteoarthritis.” World journal of orthopedics vol. 8,1 1-11. 18 Jan. 2017, DOI: 10.5312/wjo.v8.i1.1
  2. Baron, A. D., et al. “Glucosamine induces insulin resistance in vivo by affecting GLUT 4 translocation in skeletal muscle. Implications for glucose toxicity.” The Journal of clinical investigation 96.6 (1995): 2792-2801.
  3. Biggee, Beth A., et al. “Effects of oral glucosamine sulphate on serum glucose and insulin during an oral glucose tolerance test of subjects with osteoarthritis.” Annals of the rheumatic diseases 66.2 (2007): 260-262.
  4. Knudsen, James F., and Gerald H. Sokol. “Potential Glucosamine‐Warfarin interaction resulting in increased international normalized ratio: Case report and review of the literature and MedWatch database.” Pharmacotherapy: The Journal of Human Pharmacology and Drug Therapy 28.4 (2008): 540-548.
  5. Rozenfeld, Vitalina, Judy L. Crain, and A. Kevin Callahan. “Interaction of warfarin with glucosamine—chondroitin.” American journal of health-system pharmacy 61.11 (2004): 1186-1186.
  6. Anderson, J W et al. “Glucosamine effects in humans: a review of effects on glucose metabolism, side effects, safety considerations and efficacy.” Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association vol. 43,2 (2005): 187-201.
  7. Fox, Beth Anne, and Mary M Stephens. “Glucosamine hydrochloride for the treatment of osteoarthritis symptoms.” Clinical interventions in aging vol. 2,4 (2007): 599-604.
Sony Sherpa (MD)
Sony Sherpa is a board-certified clinical doctor and currently, she is working as a medical officer in the emergency department of a renowned hospital. With a medical degree completed at a young age, she writes medical articles with accuracy owing to her medical knowledge and thorough background research.