Forskolin is a plant compound (a labdane diterpene) found in the roots of Coleus forskohlii, a member of the mint family native to India. In laboratory studies it switches on adenylyl cyclase, the enzyme that makes the signaling molecule cyclic AMP (cAMP). As a dietary supplement it is sold mainly as a “fat burner,” and sometimes as a testosterone booster.

The human evidence is thin. Only a handful of small randomized trials have tested oral C. forskohlii extract, each with 60 or fewer participants and lasting 12 weeks. They gave mixed results: one found less body fat in overweight men, two found no significant difference in weight versus placebo, and a 2026 manufacturer-run trial reported about 1.9 kg more weight loss. A 2026 systematic review called the weight-loss findings inconsistent. The US Federal Trade Commission has also acted against marketers who sold forskolin with false weight-loss claims.

This page summarizes what the clinical trials, laboratory studies and the FTC record report. It is for education only and is not medical advice.

Property	Detail
Class	Labdane diterpene from Coleus forskohlii root
Formula	C₂₂H₃₄O₇, molecular weight 410.5 g/mol (PubChem)
Main action (lab)	Directly activates adenylyl cyclase, raising cellular cAMP
Form studied in trials	250 mg of root extract standardized to 10% forskolin, twice daily, for 12 weeks
Route	Oral (supplement); intravenous forskolin was studied experimentally in heart failure
Half-life	No published human pharmacokinetic data for oral supplements found
US status	Sold as a dietary supplement; not an FDA-approved drug
FTC	2017 settlement with marketers of “Original Pure Forskolin” over false weight-loss claims
WADA	Not named on the 2026 Prohibited List

What it is

Forskolin’s chemical name describes a three-ring labdane skeleton carrying an acetate group, three hydroxyl groups and a vinyl group (PubChem CID 47936). The trials below did not use pure forskolin. They used an extract of the dried root standardized to 10% forskolin. A 250 mg capsule of such an extract therefore holds about 25 mg of forskolin, alongside many other plant compounds.

Mechanism: adenylyl cyclase activation (laboratory data)

A 1981 study reported that forskolin activates adenylyl cyclase in rat brain membranes and in intact rat brain tissue slices (Seamon et al., PNAS 1981). Key findings from that study:

Finding (rat tissue, in vitro)	Result
Concentration for half-maximal activation (membranes)	5–10 µM
cAMP rise in cerebral cortex slices	About 35-fold, rapid and reversible
Need for receptor or G-protein stimulation	Not required; acts directly on the enzyme
At low concentration (1 µM)	Amplified cAMP responses to norepinephrine, adenosine and other signaling molecules

This is the main argument for forskolin as a weight-loss ingredient: the authors of one trial describe forskolin raising cAMP and fat breakdown (lipolysis) in cell and animal studies (Loftus et al., Nutrients 2015). These are laboratory effects at defined concentrations. Whether the amount of forskolin absorbed from a 25 mg oral dose reaches such concentrations in human fat tissue has not been shown.

Other effects seen in people and in the lab

Because cAMP also relaxes smooth muscle and strengthens heart contraction, forskolin was studied as a drug in the 1980s and 1990s:

Heart failure (intravenous). In 12 patients with severe congestive cardiomyopathy, intravenous forskolin dose-dependently reduced preload and afterload, lowered pulmonary artery and wedge pressures by more than 50%, and increased stroke volume by about 70% (Baumann et al., J Cardiovasc Pharmacol 1990). In 15 patients with dilated cardiomyopathy, intravenous forskolin acted mainly by lowering preload, with less benefit than dobutamine (Kramer et al., Arzneimittelforschung 1987).
Platelets (cell studies). In washed human platelets, forskolin blocked the calcium rise and the clumping (aggregation) triggered by thrombin and platelet-activating factor (Sage & Rink, FEBS Lett 1985).
Asthma (oral). In a single-blind trial of 60 adults with mild or moderate asthma, 10 mg/day oral forskolin for 2 months did not significantly improve any lung function measure (Huerta et al., J Int Med Res 2010).

How it works in the body

We found no published human pharmacokinetic study of oral forskolin or C. forskohlii extract: absorption, blood levels, half-life and metabolism after a supplement dose are not established. Studies in mice suggest that the whole extract does more than forskolin alone (see “Liver enzymes and drug interactions” below).

What the research shows

Weight and body composition trials

We found four placebo-controlled trials of oral C. forskohlii extract in PubMed. All used 250 mg of extract standardized to 10% forskolin, twice daily, for 12 weeks.

Trial	Participants	Design	Main result vs placebo
Godard et al., Obes Res 2005	30 overweight or obese men (15 vs 15)	Randomized, double-blind	Body fat % and fat mass fell significantly (DXA); lean mass only a trend (p = 0.097)
Henderson et al., JISSN 2005	19 mildly overweight women analyzed (7 extract vs 12 placebo)	Randomized, double-blind	No significant difference in fat mass, fat-free mass or body fat %; weight change −0.7 vs +1.0 kg (p = 0.10)
Loftus et al., Nutrients 2015	30 overweight or obese adults completed (15 vs 15) of 41 enrolled; both groups on a reduced-calorie diet	Randomized, double-blind	No significant difference in weight or body measurements; insulin and insulin resistance improved more with extract
Channangihalli Thimmegowda et al., JISSN 2026	60 overweight adults (30 vs 30; 50 women)	Quasi-randomized, double-blind	Body weight −1.93 kg and waist −1.83 cm vs placebo

Some details matter when reading these results:

Godard 2005 reported significant fat loss on DXA (a body-composition scan) but no significant change in total body weight, as later trial authors noted (Loftus et al., Nutrients 2015). It also reported an increase in bone mass versus placebo.
Henderson 2005 concluded that the extract “does not appear to promote weight loss” but may blunt weight gain. Women on the extract reported less hunger and fullness. The extract and placebo were supplied by Sabinsa, which also part-funded the study.
Loftus 2015 found that waist and hip circumference fell and HDL rose in both groups, so those changes reflect the diet, not the extract. The extract was supplied by its manufacturer, Olive Life Sciences.
Channangihalli Thimmegowda 2026 tested a branded extract, Forcslim. The first two authors work in the research department of Star Hi Herbs, which prepared the product. The paper declared no funding and no conflicts of interest. Allocation was “quasi-randomized” rather than truly randomized, a weaker design.

Systematic reviews

A systematic review published online in October 2026 searched five databases up to May 2023 and found only four randomized controlled trials (Nikkhah et al., J Integr Complement Med 2026). The authors concluded:

the extract “may” reduce fat mass and body fat percentage;
findings on weight loss and overall body composition were inconsistent;
adverse effects were generally mild and infrequent;
high-quality, long-term, double-blind trials are still needed.

The abstract reports no pooled effect size, and the search ended before the 2026 Forcslim trial was published.

Testosterone

Forskolin is often marketed for testosterone. Only one controlled trial has measured it, the 30-man Godard study (Godard et al., Obes Res 2005):

Measure	Forskolin	Placebo	Significant?
Serum free testosterone	Increased	—	Yes (p ≤ 0.05)
Serum total testosterone, % change	+16.77 ± 33.77%	−1.08 ± 18.35%	No

The standard deviation of the total testosterone change (±33.77%) was twice the average change itself, meaning the response varied widely between men. The trial included only overweight or obese men and was not designed to test muscle or strength. No later trial has replicated the free-testosterone finding, and none has tested forskolin in lean, trained men or in men with low testosterone.

About “forskolin boosts testosterone.” The claim rests on one 12-week trial in 15 men taking the extract. Free testosterone rose, total testosterone did not change significantly, and lean mass showed only a non-significant trend. That is a hypothesis, not evidence of an anabolic effect.

Side effects and risks

What the oral trials reported

The four trials reported few side effects at 250 mg twice daily for 12 weeks:

Henderson 2005: no clinically significant changes in heart rate, blood pressure, liver or muscle enzymes, blood lipids, blood counts, thyroid hormones, or weekly side-effect reports.
Loftus 2015: two people on the extract had gastrointestinal effects in the first three weeks (one had more frequent bowel movements, one loose stools), which resolved by week 4.
Channangihalli Thimmegowda 2026: no clinically significant changes in liver or muscle enzymes, heart rate or blood pressure.

These trials were small, short, and mostly excluded people with heart, liver or kidney disease, so they cannot detect uncommon harms.

Blood pressure and bleeding: what is known

There are plausible reasons for caution, but no human interaction studies:

Blood pressure. Intravenous forskolin is a strong vasodilator in heart-failure patients (see above). Oral supplement trials did not find blood-pressure changes, but none enrolled people taking blood-pressure medicines. The Loftus trial excluded people taking medication for hypertension or for thrombocytosis (high platelet counts), and people prone to peptic ulcers (Loftus et al., Nutrients 2015).
Bleeding. Forskolin inhibits platelet aggregation in human platelets in the test tube. Whether oral supplements do this in people, or add to the effect of anticoagulant or antiplatelet drugs, has not been studied.

Liver enzymes and drug interactions (animal and cell data)

Japanese researchers have repeatedly found that C. forskohlii extract induces liver drug-metabolizing enzymes in animals:

In mice, the crude extract induced liver cytochrome P450 (CYP) enzymes and caused fatty liver, while pure forskolin did not; the fatty-liver effect was traced to another compound in the extract, 14-deoxycoleon U (Umegaki et al., J Oleo Sci 2019).
In mice, the extract induced CYP3A in the liver at a dietary level of 0.005% and in the small intestine only at 0.5%, and the induction reversed after the extract was stopped (Yokotani et al., Biol Pharm Bull 2020).
In cell culture and humanized mice, C. forskohlii extract strongly activated the human CYP3A4 gene; forskolin raised CYP3A4 expression 3.9-fold in mice engineered to carry the human genes (Adachi et al., Yonago Acta Med 2024). The authors linked this to a patient’s acute liver injury while taking several slimming products and drugs.

CYP3A4 breaks down many prescription drugs. These findings suggest a possible interaction mechanism, but they come from animals and cells, not controlled human studies.

Groups without safety data

No trial has studied forskolin in people taking blood-pressure medicines, anticoagulants or antiplatelet drugs, or drugs broken down by CYP3A4, or in people with liver disease. Pregnant and breastfeeding women were excluded from the Loftus and 2026 trials.

Legal status and marketing

FTC action against forskolin weight-loss marketing

In 2017, the FTC settled charges against Colby Fox and his companies Tachht, Inc. and Teqqi, LLC, affiliate marketers of “Original Pure Forskolin” and “Original White Kidney Bean” (FTC, March 17, 2017). According to the FTC:

the defendants paid affiliates to send millions of spam emails from hacked accounts, so they appeared to come from friends and family;
the emails led to fake news sites claiming losses such as “41.7lbs in 2.5 months” and falsely suggesting endorsements by Oprah Winfrey and the hosts of “The Doctors”;
the FTC alleged the weight-loss claims were “false and unsubstantiated.”

The defendants agreed to pay $500,000 against a judgment of $1,303,822.98, and the order requires competent and reliable scientific evidence for future health claims. Litigation against a fourth defendant, Christopher Reinhold, continued at the time. In March 2018, the FTC mailed 18,301 refund checks totaling more than $437,000 to buyers of these products (FTC, March 15, 2018).

Sport

Forskolin is not named on the WADA 2026 Prohibited List. As with any supplement, the label may not match the contents.

Forskolin is commonly sold alongside other “fat burner” ingredients. Green tea extract has a larger evidence base, including a Cochrane review, and a documented liver-safety signal at high EGCG doses.

Key takeaways

A lab tool first. Forskolin directly activates adenylyl cyclase and raises cAMP in cells, which is why it is used widely in research. That does not show it burns fat when taken as a supplement.
Few, small trials. Four 12-week trials of 19–60 people tested 250 mg of 10% extract twice daily. One found less body fat in men, two found no significant weight difference, and a manufacturer-run 2026 trial reported about 1.9 kg more weight loss.
Reviewers call the evidence inconsistent. A 2026 systematic review found only four RCTs and called for larger, longer, higher-quality trials.
Testosterone claim rests on one study. In 15 men, free testosterone rose but total testosterone did not change significantly.
Short-term tolerability looks good, but interactions are unstudied. Trials reported few side effects. Intravenous vasodilation, in-vitro platelet inhibition and CYP3A induction in animals raise unanswered questions for people on blood-pressure drugs, anticoagulants or CYP3A4-metabolized drugs.
Marketing has outrun the science. The FTC settled a case in 2017 against marketers who used spam, fake news sites and false celebrity endorsements to sell forskolin.

Sources

Seamon KB, Padgett W, Daly JW. Forskolin: unique diterpene activator of adenylate cyclase in membranes and in intact cells. Proc Natl Acad Sci U S A. 1981;78(6):3363–3367. PubMed.
National Center for Biotechnology Information. Forskolin, PubChem CID 47936. PubChem.
Godard MP, Johnson BA, Richmond SR. Body composition and hormonal adaptations associated with forskolin consumption in overweight and obese men. Obes Res. 2005;13(8):1335–1343. PubMed.
Henderson S, Magu B, Rasmussen C, Lancaster S, et al. Effects of coleus forskohlii supplementation on body composition and hematological profiles in mildly overweight women. J Int Soc Sports Nutr. 2005;2(2):54–62. PubMed; PMC.
Loftus HL, Astell KJ, Mathai ML, Su XQ. Coleus forskohlii extract supplementation in conjunction with a hypocaloric diet reduces the risk factors of metabolic syndrome in overweight and obese subjects: a randomized controlled trial. Nutrients. 2015;7(11):9508–9522. PubMed; PMC.
Channangihalli Thimmegowda S, Hussain Mirza FH, Venkataraman R, Nagarajaiah RB. A 12-week, double-blind, quasi-randomized, placebo-controlled study to evaluate the efficacy and safety of Coleus forskohlii (Forcslim) on body weight loss. J Int Soc Sports Nutr. 2026;23(1):2725137. PubMed; PMC.
Nikkhah E, Ostadrahimi A, Rahimi S, Radkhah N, et al. The effectiveness and safety of Coleus forskohlii extract as an anti-obesity agent: a systematic review. J Integr Complement Med. Published online October 8, 2026. doi:10.1177/27683605261492576. PubMed.
Baumann G, Felix S, Sattelberger U, Klein G. Cardiovascular effects of forskolin (HL 362) in patients with idiopathic congestive cardiomyopathy: a comparative study with dobutamine and sodium nitroprusside. J Cardiovasc Pharmacol. 1990;16(1):93–100. PubMed.
Kramer W, Thormann J, Kindler M, Schlepper M. Effects of forskolin on left ventricular function in dilated cardiomyopathy. Arzneimittelforschung. 1987;37(3):364–367. PubMed.
Sage SO, Rink TJ. Inhibition by forskolin of cytosolic calcium rise, shape change and aggregation in quin2-loaded human platelets. FEBS Lett. 1985;188(1):135–140. PubMed.
Huerta M, Urzúa Z, Trujillo X, González-Sánchez R, et al. Forskolin compared with beclomethasone for prevention of asthma attacks: a single-blind clinical trial. J Int Med Res. 2010;38(2):661–668. PubMed.
Umegaki K, Yokotani K, Marumoto S, Miyazawa M. Identification of compounds in Coleus forskohlii extract involved in the induction of hepatic CYP and fatty liver in mice. J Oleo Sci. 2019;68(10):995–1002. PubMed.
Yokotani K, Yamazaki Y, Shimura F, Umegaki K. Comparison of CYP induction by Coleus forskohlii extract and recovery in the small intestine and liver of mice. Biol Pharm Bull. 2020;43(1):116–123. PubMed.
Adachi M, Kumagai T, Hosho K, Nagata K, et al. Exploring acute liver damage: slimming health foods and CYP3A4 induction. Yonago Acta Med. 2024;67(2):124–134. PubMed.
Federal Trade Commission. FTC settlement bars spam email marketing, baseless weight-loss claims by diet-pill operation. Press release, March 17, 2017. FTC.
Federal Trade Commission. FTC sending refund checks totaling more than $437,000 to consumers who bought bogus weight-loss products. Press release, March 15, 2018. FTC.
World Anti-Doping Agency. World Anti-Doping Code International Standard: Prohibited List 2026. In effect from January 1, 2026. WADA 2026 Prohibited List.

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