FDA has warned consumers that although products containing CBD (cannabidiol) are widely available, they may not be safe. While the agency is working to "answer questions about the science, safety, and quality of products containing cannabis, and cannabis-derived compounds including CBD," much remains uncertain.

FDA is concerned that people taking CBD may have adverse effects, including liver injury, effects on the metabolism of other drugs, and increased sedation or drowsiness if taken with other drugs such as alcohol or other CNS depressants.

The agency has approved CBD for only one use so far, a prescription medication for a rare form of epilepsy. FDA noted that it is currently illegal to market CBD by adding it to a food or dietary supplement. No uses have been approved for animals. Among other issues, FDA is investigating the safety of CBD in animals, including both pets and food-producing animals.

FDA has also issued warning letters to 15 companies, telling them that they are violating federal law by adding CBD to human foods, nutritional supplements, and animal foods and for marketing unapproved human and animal drugs containing CBD.

More details on the FDA consumer warning on CBD products are available from CNBC. The full FDA announcement on CBD can be read here.

More information on the toxicity of cannabis in animals is available in the MSD Veterinary Manual.