Bitter orange (Citrus aurantium) is a citrus tree whose fruit contains p-synephrine, a chemical similar in structure to ephedrine but with different effects in the body. Bitter orange supplements are promoted for weight loss and sports performance, and became more popular as an ephedra alternative after FDA banned ephedra in supplements in 2004.
Also known as: Citrus aurantium, p-synephrine, synephrine, Seville orange, sour orange, zhi shi.
Bitter orange has no intake value or upper limit. NCCIH reports that in an FDA analysis of 59 bitter orange supplements, only 5 of the 23 products that listed a synephrine amount were within 80% to 120% of it, and 6 contained synthetic amines (methylsynephrine or isopropyloctopamine) that are not legal dietary ingredients.
It is sold in the US as a dietary supplement. Under the 1994 dietary supplement law (DSHEA), FDA does not approve dietary supplements before they are marketed, and the maker, not FDA, is responsible for safety and labeling.
Evidence, per NCCIH: bitter orange has not been clearly shown to help with any health purpose. Weight loss studies were small, mostly tested combination products, and had conflicting results; most small studies on athletic performance found no benefit.
Safety: NCCIH says amounts in food are likely safe, but serious events including abnormal heart rhythms, heart attacks and strokes have been reported in people taking bitter orange products. Most of those products had several ingredients, so it is unclear whether bitter orange caused them, and studies disagree on whether it raises blood pressure and heart rate. It may not be safe in pregnancy or breastfeeding. In sport, the NCAA bans synephrine (bitter orange) as a stimulant (NCCIH); WADA's 2026 list places synephrine in its Monitoring Program, which means it is not prohibited. See also ephedrine.
We could not find a published half-life or time to peak for bitter orange that we could cite, so we do not list one. Label amounts of synephrine are often inaccurate (NCCIH).
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