What is Glucosamine?
Glucosamine is a naturally occurring chemical compound that can be found in both human and animal tissues. One of its essential functions in humans is its contribution to the formation of cartilage. Cartilage is a crucial connective tissue that covers the bony surfaces of joints and provides cushioning and shock absorption. Osteoarthritis is a degenerative joint disease that occurs when the cartilage in joints breaks down over time, leading to pain, inflammation, and joint stiffness. Glucosamine supplements are commonly used as a dietary supplement to manage joint disorders like osteoarthritis.
Glucosamine is believed to slow cartilage decay, relieve joint pain (especially for people suffering from osteoarthritis) and reduce inflammation. IIt has been shown to lower C-reactive protein (a biomarker of inflammation) in small studies. Glucosamine and chondroitin have been found to inhibit inflammatory pathways in human synovial cells, although it's unclear if they have localized anti-inflammatory effects. Glucosamine's anti-inflammatory properties may also lower the risk of developing conditions mediated by inflammation, like type 2 diabetes.
Anyone who’s ever been through serious joint pain will probably agree that one doesn’t feel like waiting for pain relief any longer than necessary. Certain individuals can’t just take nonsteroidal anti-inflammatory drugs for treating joint pain (including those who have a history of allergic reactions to NSAIDs or aspirin, those with a history of stomach ulcers or bleeding disorders, individuals with kidney or liver problems, as well as pregnant women and those who are breastfeeding) and their biggest hope lies in glucosamine sulfate! So it’s no wonder the user forums and health blogs are full with people asking the question: “How long does it actually take for glucosamine to work?”
In case you just took the first dose of glucosamine, eagerly waiting for pain relief, we might disappoint you right away: Various scientific studies came to different results regarding the effectiveness of glucosamine and the time it needs to show its potential effects. While some studies found glucosamine rather ineffective, most researchers came to the conclusion that it takes from three weeks up to 2 months until you can expect any noticeable effects.  So if you don’t feel any improvement after 8 weeks, chances are you belong to the small group of non-responders.
This doesn’t mean glucosamine can’t be beneficial for you over time or under different conditions, though! Depending on how serious the respective joint disease is and which category it belongs to exactly, it might simply take more time for you to feel an effect. If you suffer from heavy arthrosis for example, it’s not unusual for glucosamine to take a few weeks longer to kick in. Furthermore, you might expect too much of a miracle drug as well. Remember that glucosamine is not an opioid or any other fast-acting pain killer (though it might help with morphine tolerance and dependency!) but an amino sugar that does not work on the nervous system.
Dosage And Types Of Glucosamine
The typical glucosamine dosage is 1,500-3,000 mg per day, and it is available in three supplement forms: glucosamine sulfate, glucosamine hydrochloride, and N-Acetyl glucosamine. Studies have shown that glucosamine sulfate is effective in improving osteoarthritis symptoms. It can be taken at once or in smaller doses. Glucosamine supplements are made from natural sources like shellfish shells or fungi or manufactured artificially in a lab.
Glucosamine sulfate is commonly sold in combination with chondroitin sulfate, which studies suggest increases it's efficacy, and used to treat bone and joint conditions, particularly osteoarthritis, rheumatoid arthritis, and osteoporosis. Doctors often combine these with omega 3 on top to increase the positive effects.
Glucosamine HCL is purer  and some studies suggest it's more effective or can be taken in a smaller dose, however it does come with increased risk of side effects.
The none shellfish version, typically from corn has been shown to be as effective as glucosamine sulfate, although there have been less studies overall. 
The most common dosage is 1500mg of glucosamine sulfate. 
Other health conditions glucosamine might help with
In addition to its traditional use for joint pain and osteoarthritis, some people take glucosamine supplements for a variety of other health conditions. These conditions include interstitial cystitis (IC), inflammatory bowel disease (IBD), multiple sclerosis (MS), glaucoma, and temporomandibular joint (TMJ) disorders.
Q: Does glucosamine really work for pain? A: Glucosamine has been found to be effective in reducing joint pain for some people, especially those with osteoarthritis.
Q: Is it OK to take glucosamine everyday? A: It's generally safe to take glucosamine supplements every day, but it's essential to follow the recommended dosage on the product label or consult with a healthcare professional to determine an appropriate dosage for your specific needs.
Q: How many days should I take glucosamine? A: There is no specific timeframe for taking glucosamine, as some people may experience pain relief within a few weeks, while others may need more time. It's important to be patient and consistent with the recommended dosage for at least three months to determine if it's working for you.
Q: What time of day should I take glucosamine? A: Glucosamine is typically taken with meals, and it doesn't matter what time of day you take it. However, be sure to follow the manufacturer's instructions or the advice of a healthcare professional for the best results.
Q: Should glucosamine be taken before or after food? A: It is recommended to take glucosamine with or after food. Taking it on an empty stomach may cause stomach upset or discomfort.
Q: Is it better to take glucosamine on an empty stomach? A: No, it is not better to take glucosamine on an empty stomach. It is recommended to take glucosamine with or after a meal to minimize the risk of stomach upset or discomfort.
Q: Can glucosamine be taken with other vitamins? A: Yes, glucosamine can be taken with other vitamins. However, it is always important to read the label of the product and consult with a healthcare provider before adding any new supplements to your regimen. Some vitamins and supplements may interact with glucosamine or have side effects that should be considered.
2 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2686334/
3 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9370395/
4 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3086604/