Synephrine
Synephrine comes from bitter orange. In randomised research, 2 to 3 mg per kilo of body weight shifted fuel selection toward fat during low to moderate intensity exercise. Total energy expenditure stayed unchanged, both at rest and during exercise.
What the research shows
Mixed or small evidence. The effect is uncertain.
The human research comes almost entirely from one Spanish group and measures fat oxidation during exercise, a surrogate outcome. Gutiérrez-Hellín and Del Coso (2018) saw higher fat oxidation at 3 mg per kilo of body weight with no change in performance, and the trial in active women (2022) showed the same pattern. The 2021 review by the same group states that no trial has demonstrated actual weight or fat loss. The two studies whose funding is documented were paid for by Spanish universities, so this is independent work; the evidence simply stops at a surrogate measure.
Who it makes sense for: People who want to burn a little more fat during endurance work and accept that no study has turned that into weight loss. Nothing was found for strength, sprinting or endurance. Leave it alone with high blood pressure or heart problems, certainly alongside a large caffeine dose.
How we weigh evidenceClinical dosage
Origin
NaturalSynephrine naturally occurs in bitter orange (Citrus aurantium), also known as Seville orange. It's found in the peel and traditionally used in Chinese medicine as zhi shi.
Safety
At the doses studied, heart rate and blood pressure stayed unchanged. Two things to know: the effect is small and concerns the ratio between fat and carbohydrate rather than extra burning, and in a study of 18 women it was not reproduced. The studied dose of 1 to 3 mg per kilo works out to 70 to 225 mg, more than most pre-workouts contain.
For comparison
A bitter orange contains about 6mg of synephrine. A pre-workout with 30mg synephrine equals about 5 bitter oranges. The metabolic effect is comparable to a strong cup of green tea.
Dosage by weight and gender
The effective synephrine dose is 20-50mg per day for fat burning and energy (Stohs et al., 2012). Body weight plays a limited role. Start with a low dose (20mg) and build up. No significant differences between men and women have been reported.
Frequently asked questions
What does synephrine do?
Synephrine activates beta-3 adrenergic receptors, increasing metabolism and fat burning. It works as a milder, more targeted version of ephedrine. It can also improve energy performance during training.
Is synephrine dangerous?
At the recommended dose (20-50mg), synephrine is safe for healthy adults. A review by Stohs et al. (2012) confirms p-synephrine doesn't significantly raise heart rate or blood pressure. Don't combine it with large amounts of caffeine or other stimulants.
How much synephrine per day?
20-50mg per day, preferably split into 2-3 doses. Take it 30 minutes before training or between meals. Don't exceed 50mg per day, especially if you also use caffeine.
Scientific sources
The clinical dosages on this page are based on peer-reviewed research.
- Dose-Response Effects of p-Synephrine on Fat Oxidation Rate During Exercise of Increasing IntensityGutiérrez-Hellín J et al. (2018)
- Effects of p-Synephrine during Exercise: A Brief Narrative ReviewRuiz-Moreno C et al. (2021)Funded by: Geen externe financiering; de publicatiekosten zijn betaald door Camilo José Cela University.
- Effect of p-Synephrine on Fat Oxidation Rate during Exercise of Increasing Intensity in Healthy Active WomenGutiérrez-Hellín J et al. (2022)Funded by: Gefinancierd door Universidad Francisco de Vitoria, subsidie UFV-18/2020.
Pre-workouts with Synephrine
5% Nutrition 5150
2 flavors
Hardcore pre-workout with 400mg caffeine from multiple sources, 4g citrulline, and 2.5g beta-alanine. Not for beginners — one of the strongest pre-workouts on the market.
We keep the dosages and values on this page as accurate as possible based on selected studies. New research may change these values. Nothing on this page is medical advice. If you have any doubts, always consult a doctor.