Raspberry Ketones for Weight Loss: Never Tested Alone in People

There is no human evidence that raspberry ketone causes weight loss. No randomized trial has ever given people raspberry ketone by itself. The two small trials usually cited tested a capsule that also contained caffeine, capsaicin and bitter orange, on top of a diet and exercise program.^[2][3] The rest of the case comes from cells and rodents fed doses no one gets from fruit,^[1][9] and the best-controlled mouse study found that the animals mostly just ate less.^[10] Doses large enough to suppress appetite in mice also caused organ damage and deaths.^[11]

What raspberry ketone is

Raspberry ketone is the compound that gives red raspberries much of their smell. Chemists call it 4-(4-hydroxyphenyl)-2-butanone. The food and cosmetics industries have used it for decades as a flavor and fragrance, and it appears on FDA’s list of synthetic flavoring substances that may be used in food in “the minimum quantity required to produce their intended effect.”^[18] An industry fragrance panel found it was not genotoxic and raised no concern at the levels used in perfumes and cosmetics.^[20]

That flavoring history is not a safety record for capsules. Raspberries contain at most about 4.3 mg of raspberry ketone per kilogram of fruit, and supplements have been sold with recommended doses of 100 to 1,400 mg a day.^[14] The low end of that range is what you would get from roughly 23 kg of raspberries. The high end is the ketone in about 326 kg. Nearly all of it in capsules is made synthetically, and the label is not always accurate: a 2025 laboratory analysis found that 60% of supplements declaring a raspberry ketone content did not match their labels, most of them containing less than stated.^[16]

Despite the name, raspberry ketone has nothing to do with ketosis. It is structurally unrelated to the ketone bodies that rise on a ketogenic diet or during fasting, and taking it does not put you in ketosis.^[19]

The evidence, sorted by what was actually tested

The animal studies the claim rests on

The story starts with a 2005 Japanese study. Mice were fed a high-fat diet with raspberry ketone mixed in at 0.5%, 1% or 2% of their food for 10 weeks. They gained less weight and less abdominal fat than mice on the same diet without it. In fat cells taken from rats, the compound boosted the breakdown of stored fat triggered by norepinephrine. The authors noted that raspberry ketone looks chemically like capsaicin and synephrine, two compounds already linked to fat metabolism.^[1] A 2010 study in mouse fat cells grown in a dish found more fat breakdown and fat burning at a concentration of 10 micromolar.^[9]

Feeding a compound as 1% or 2% of a mouse’s diet is an enormous dose, and the design of the first study left an obvious question open: did the mice simply eat less? An Ohio State team tested exactly that in 2017. They added a pair-fed group, mice given the same amount of food as the raspberry ketone mice but no raspberry ketone. The treated mice did eat less and weigh less than controls. Compared with the pair-fed mice, though, the low dose made no difference to fatty liver, and the authors concluded raspberry ketone “has limited benefit to adipose loss beyond reducing energy intake.” Their own summary of the field was that there is “scant scientific evidence” it promotes weight loss.^[10]

A Rutgers group then measured the appetite effect directly and found the problem with it. Given by stomach tube, raspberry ketone cut 24-hour food intake by 24% at 200 mg/kg in male mice and by 49 to 77% at 640 mg/kg. At 640 mg/kg, a single dose killed 6 of 14 male mice within two days. Survivors showed shrunken fat tissue, abnormalities of the spleen and thymus, and changes in white and red blood cells. The researchers concluded that the doses that reliably suppress eating are associated with pathological changes.^[11] In a second study, 400 mg/kg a day for two weeks reduced weight gain but also lowered blood pressure and how much the mice moved around.^[12] The compound is absorbed within about 15 minutes in mice, and obese mice had nearly double the blood exposure of lean ones.^[13]

The two human trials, and why they cannot answer the question

Only two randomized trials in people have included raspberry ketone, and both tested the same kind of product: a multi-ingredient capsule containing raspberry ketone alongside caffeine, capsaicin, garlic, ginger and Citrus aurantium, the bitter orange extract that supplies synephrine.^[2][3]

In the 2013 trial, 70 adults with obesity were randomized to the capsule or a rice-flour placebo for eight weeks, with a calorie-restricted diet and exercise training for everyone. Only 45 finished. Among them, the capsule group lost 2.0% of body weight and the placebo group 0.5%, and fat mass fell 7.8% against 2.8%.^[2] The study was sponsored by the product’s maker, Ultimate Wellness Systems, and two of the authors disclosed research funding or consulting for supplement companies including that sponsor. The paper states that the sponsor had no role in collecting or analyzing the data.^[2]

The 2018 trial, which shared authors with the first, put 36 adults with overweight on the same kind of program with a similar capsule or placebo. Both groups lost about 2.6 kg of weight and 1.8 kg of fat over eight weeks. The differences that favored the capsule were secondary: more lean mass gained in the men, a larger drop in hip measurement in the women, and changes in the hormones leptin and adiponectin.^[3]

Neither trial can say anything about raspberry ketone. Caffeine and synephrine are stimulants with their own effects on energy expenditure, and capsaicin has been tested and failed as a weight-loss ingredient on its own (see capsaicin and capsinoids). With six active ingredients in one capsule, any difference between the groups could come from any of them. A 2021 review of the whole literature put it plainly: raspberry ketone is sold at very high doses despite a lack of reliable human research.^[17]

How a raspberry aroma became a diet pill

Raspberry ketone’s run as a diet pill was driven by daytime television. When the Senate consumer protection subcommittee held a hearing on weight-loss advertising on June 17, 2014, Senator Claire McCaskill read back a line the television physician Mehmet Oz had used on his show: “I’ve got the number one miracle in a bottle to burn your fat. It’s Raspberry Ketone.” She told him the scientific community was “almost monolithic” against him on the efficacy of the products he had called miracles.^[4] At the same hearing, the head of the advertising industry’s self-regulatory body told senators it had handled a similar case over raspberry ketone advertising claims.^[4]

Marketers moved fast. One Atlanta company added a product called Healthe Trim Powered by Raspberry Ketone in September 2012. A radio ad for it promised “You’ll lose weight without dieting” and said it “burns the fat, suppresses your appetite, and will boost your energy.” By the end of 2013, sales of the company’s product line, net of refunds, exceeded $76 million.^[6]

What the Federal Trade Commission did

• HealthyLife Sciences (2014). The FTC charged the Healthe Trim marketer with false or unsupported claims across its line, including the raspberry ketone formula: weight loss of as much as 165 pounds, weight loss without dieting, fat burning, a faster metabolism and appetite suppression. Under the September 2014 settlement, the company’s co-founder was banned from manufacturing or marketing weight-loss products.^[5][6]
• Tarr, Inc. (2017). The FTC sued a group of online marketers that sold more than 40 weight-loss, muscle and anti-wrinkle products through fake news and magazine sites. One page sold “Flawless Raspberry Ketone” as a miracle pill with a fabricated endorsement from the celebrity cook Paula Deen, who had no connection to it. The order imposed a $179 million judgment, suspended once the defendants paid about $6.4 million.^[7][8]

Neither case turned on whether raspberry ketone is dangerous. They turned on whether the sellers could back up their claims, and they could not. The same fake-endorsement and fake-news playbook has since moved on to newer ingredients, including the “GLP-1” supplements covered in our review of GLP-1 supplements.

Is raspberry ketone safe?

Nobody knows at supplement doses, because it has not been studied properly. A 2015 review by Denmark’s National Food Institute found that toxicity data were limited to short-term rat studies. Even the lowest recommended supplement dose of 100 mg a day was 56 times the generic safety threshold used for a compound of its class, and the margin of safety against the highest dose that did not slow weight gain in rats fell to 12 at 1,400 mg a day. Computer models flagged possible effects on the heart and on reproduction and development. The authors said its toxic potential needed to be clarified, and noted that the U.K. treated the pure compound as a novel food that needs approval before it can be sold.^[14]

There is one published human case report of a serious reaction. A 47-year-old woman in England arrived at hospital with diarrhea, sweating, a heart rate of 137 and blood pressure of 197/130 about two hours after taking two raspberry ketone tablets for the first time. Over the next days she had six episodes of chest pain with ECG changes that looked like a heart attack, each resolving within minutes with nitrates. Her coronary arteries were clear on a CT scan, and her doctors diagnosed coronary artery spasm. She also had anemia, a duodenal ulcer and small blood clots in the lungs, so the link is not proven, and she was not re-challenged. The cardiologists concluded raspberry ketone, which is chemically similar to the stimulant synephrine, may be associated with coronary vasospasm.^[15]

A single case cannot establish cause, and the mouse findings come from doses far above any capsule. Together, though, they point in the same direction: a compound with stimulant-like effects, sold at doses nobody has tested for safety, with cardiovascular effects in mice and a cardiac warning flag from computer toxicity models. Anyone with heart disease, high blood pressure or an arrhythmia, anyone pregnant, and anyone taking stimulants or blood pressure medicine has particular reason to avoid it.

Raspberry ketone and GLP-1 drugs

No study has tested raspberry ketone with semaglutide or tirzepatide, and no study has found that it acts on GLP-1. There is no evidence it adds to the weight loss from those drugs. Because GLP-1 drugs already suppress appetite, adding an untested stimulant-like compound offers no known benefit and an unknown risk. If you are taking a GLP-1 drug and want to add any supplement, tell the prescriber.

For the other ingredients sold the same way, see our evidence reviews of garcinia cambogia, green tea extract and CLA. Our supplement evidence grader gives a graded entry and its primary study for sixteen more.