There are no known side effects of raspberry ketones, according to WebMD. However, raspberry ketone supplements may lower blood sugar levels and decrease bleeding, states LiveScience.
Other stimulants similar to raspberry ketone supplements point to other side effects such as jitteriness, changes in inflammation, rapid heartbeat and increased blood pressure. It is also possible that raspberry ketones may interact with medicines that regulate heart rate, cholesterol and hormones. One study found that participants who took 200 milligrams of raspberry ketone supplements and 1,200 milligrams of vitamin C for four weeks lost weight and body fat consistently. However, the U.S. Department of Defense Human Performance Resource Center does not find the evidence supporting raspberry ketones' effects on weight to be compelling. Until more information is known about raspberry ketones, WebMD suggests using more traditional weight loss methods.