There are many products promoted for weight loss that do not require a doctor's prescription. It is therefore important that you talk to your doctor or pharmacist before taking any over-the-counter products for weight loss. Many over-the-counter weight loss products contain more than one ingredient. Here is an overview of some of the more common ingredients found in these products: 5-hydroxytryptophan (5-HTP): 5-HTP is a precursor to a chemical in the brain called serotonin, which is associated with mood, sleep, appetite, temperature, and nervousness. Serotonin is thought to be involved in the regulation of food intake. There is some evidence that taking 5-HTP decreases the number of calories a person takes in each day and helps overweight or obese people to lose weight. However, larger studies are required to confirm the findings Citrus aurantium and synephrine: Citrus aurantium, also called bitter orange, is found in many non-prescription weight loss products. It should be avoided because it can lead to high blood pressure and serious heart problems. Health Canada has issued warnings against using more than 30 mg of synephrine per day. Chitosan: This ingredient reportedly decreases the absorption of fat by binding to it. It also acts as a fibre to increase feelings of fullness sooner when eating. Chitosan is derived from shellfish. Anyone with shellfish allergies should not use any products containing this agent. Recent studies suggest that chitosan does not have any effect on weight loss. Larger studies are required to confirm these findings. Conjugated linoleic acid (CLA): Thought to shrink fat tissue by causing fat cells to die, CLA is another supplement used for weight loss. Although some studies have shown that CLA does decrease body fat, most people don't lose weight while taking it. There is also some concern that CLA might increase the risk of diabetes and heart disease for people who are obese. So, the bottom line is not to use CLA for weight loss if you are obese or have heart disease until more studies are done. Calcium: Since adults and children who do not consume enough calcium are more likely to gain weight, be overweight, or be obese, calcium is receiving a lot of attention for weight loss. However, there is not enough evidence to recommend that people take calcium supplements to help with weight loss. Getting the recommended amount of calcium through your diet and supplements (if needed), though, is recommended for everyone. Green tea: Green tea extracts are commonly used for weight loss by themselves or as part of a combination product for weight loss. Green tea is derived from the leaves of Camellia sinensis. Some small studies show that green tea increases energy use and reduces food intake, but its link to weight loss is inconclusive. Guarana: Guarana is native species of South America that has stimulatory effect. When taken alone or in a combination, guarana increases energy usage. However, its link to actual weight loss is inconclusive. Rhubarb: Rhubarb has been used in traditional Chinese medicine to help with gastrointestinal problems such as constipation, diarrhea, and ulcers. It is thought to reduce food intake, prolong stomach emptying, and accelerate intestinal movement, thereby helping with weight loss. However, the evidence is conflicting in studies There are many additional weight loss products available without a prescription, but the effectiveness of these agents is not supported by clinical studies. Speak to your doctor, pharmacist, or dietitian about weight management plans and resources available in your local area. Before using any over-the-counter or herbal product, always talk to your doctor or pharmacist first. Many of these products may be harmful if used incorrectly and may interact with other medications and medical conditions. Keep in mind that health Canada recommends not to buy health products online from a company that does not provide a valid phone number and address. And, stick to products that have a drug identification number (DIN), natural product number (NPN), or homeopathic medicine number (DIN-HM). These products have been reviewed by Health Canada for their safety, effectiveness, and quality. For more information about natural products, see our natural health products database.