Coleus Forskohlii (Forskolin)
Summary
Coleus forskohlii has three small 12-week trials of 23 to 30 adults, all using 500 mg/day of a 10% forskolin extract. None found more weight loss than placebo. One found less body fat in men and one found lower insulin (grade D). NIH ODS calls the human evidence very limited and inconclusive. Loose stools are the main reported side effect; extract caused liver damage in mice.
Key facts
- Root extract of Coleus forskohlii (also called Plectranthus barbatus), standardized to the diterpene forskolin[1]
- 500 mg/day of extract standardized to 10% forskolin (about 50 mg forskolin), split before two meals, for 12 weeks[2][3][4]
- NIH ODS: human research is very limited and inconclusive; no trials longer than 12 weeks[1]
- None set; Coleus forskohlii is a herb, not a nutrient[1]
- Loose stools and more frequent bowel movements in people; dose-related liver toxicity from the whole extract in mice[1][8]
- 3 graded human outcomes on this page
- October 10, 2026
How it works
ProposedForskolin switches on adenylyl cyclase and raises cyclic AMP inside cells. Higher cAMP is thought to activate lipase and release fatty acids from fat tissue, and animal studies show reduced food intake. Whether oral extract does this in people at supplement doses is not established.[1]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
At a glance: strongest evidence per outcome
| Outcome | Grade | Effect | Strongest evidence | Rows |
|---|---|---|---|---|
| Body composition | Grade D | Improved | RCT · n = 30 · 2005 | 1 row |
| Blood sugar | Grade D | Improved | RCT · n = 30 · 2015 | 1 row |
| Body weight | Grade D | No effect | RCT · n = 23 · 2005 | 1 row |
Every graded row
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Body fat percentage and fat mass (DXA) | Improved | Grade D | RCT · n = 30 · 2005 Men with overweight or obesity (BMI 26 or higher, US) Form: Coleus forskohlii extract, 10% forskolin · Dose: 250 mg twice daily (500 mg/day) · Duration: 12 weeks Body fat percentage and fat mass fell versus placebo (p≤0.05); bone mass and free testosterone rose; lean mass showed only a trend (p=0.097). NIH ODS notes body weight did not change. | 16129715 (opens PubMed)Source [2] |
| Fasting insulin and insulin resistance | Improved | Grade D | RCT · n = 30 · 2015 Adults with overweight or obesity on a reduced-calorie diet (Australia) Form: Coleus forskohlii extract, 10% forskolin · Dose: 250 mg twice daily (500 mg/day) · Duration: 12 weeks Insulin and insulin resistance improved versus placebo (p=0.001; p=0.01). Waist and hip circumference and HDL cholesterol changed similarly in both groups, and body weight did not differ from placebo (per NIH ODS). | 26593941 (opens PubMed)Source [4] |
| Body weight and fat mass | No effect | Grade D | RCT · n = 23 · 2005 Mildly overweight women (US) Form: ForsLean (Coleus forskohlii extract, 10% forskolin) · Dose: 250 mg twice daily (500 mg/day) · Duration: 12 weeks No significant difference in body weight (p=0.10), fat mass (p=0.16) or body fat (p=0.40); the extract group reported less hunger and fullness. No clinically significant changes in blood tests, heart rate, blood pressure or side effects. | 18500958 (opens PubMed)Source [3] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| Root extract standardized to 10% forskolin (e.g. ForsLean) | Varies[1][2][3][4] | No human pharmacokinetic data in our sources.[1] | At 500 mg/day for 12 weeks, no serious adverse events were reported; loose stools and more frequent bowel movements were noted.[1][3] | All three weight and body-composition trials (500 mg/day) |
| Isolated forskolin | Varies[1][8][6] | No human absorption data in our sources.[1] | In mice, pure forskolin did not cause the liver toxicity seen with the whole extract.[1][8] | A 2-month asthma comparison (10 mg forskolin capsules daily); not weight trials |
Studied doses
Doses studied in human trials ranged from 500 to 500 mg/day: every weight and body-composition trial used 250 mg of a 10% forskolin extract twice daily for 12 weeks, about 50 mg of forskolin a day. No longer trials exist.[2][3][4][1]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
Medicines
- Drugs cleared by liver CYP enzymesPK studyIn rats, two weeks of dietary extract raised liver CYP enzyme levels and blunted the blood-sugar-lowering effect of tolbutamide. Not studied in people.[9]
Who should be careful
- Liver disease
- Whole Coleus forskohlii extract caused dose-related liver toxicity in mice; human data stop at 12 weeks.[8][1]
- Taking prescription drugs
- In rats the extract induced the liver enzymes that clear many drugs, weakening a diabetes drug.[9]
- Pregnancy and breastfeeding
- No human safety data; trials enrolled only non-pregnant adults for 12 weeks.[1][3]
- Sensitive bowels
- Forskolin may increase bowel movement frequency and cause loose stools.[1]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
Safety
Short-term human data are reassuring, but the trials were small and lasted only 12 weeks.
- Digestive effects
- More frequent bowel movements and loose stools are the side effects NIH ODS lists for forskolin.[1]
- Liver (animal data)
- Mice fed the extract developed dose-related liver toxicity; pure forskolin did not cause it.[8][1]
- Blood tests in trials
- In 12-week trials, liver enzymes, blood lipids, thyroid hormones, heart rate and blood pressure did not change in clinically significant ways.[3]
How to read the label
- Label dose vs clinical doseTrials used 500 mg/day of extract standardized to 10% forskolin, about 50 mg of forskolin. A label listing only "forskolin 125 mg" or a different percentage is not the studied dose.[2][3][4]
- Extract vs pure forskolinThe mouse liver toxicity came from the whole root extract, not from pure forskolin, so other plant compounds may be involved.[1][8]
- Weight-loss blendsMany products combine forskolin with stimulants and other ingredients; the trials here tested the extract alone.[2][3][4]
Cost per studied dose, without the sales pitch
Compare any product you already have by the amount it delivers, not by capsule count or front-of-pack weight.
Cost per studied dose
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Frequently asked questions
Does forskolin help with weight loss?
Not in the trials so far. Three 12-week trials using 500 mg/day of a 10% extract found no more weight loss than placebo. One found less body fat in men; NIH ODS calls the evidence very limited and inconclusive.[1][2][3][4]
How much Coleus forskohlii was used in studies?
250 mg of extract standardized to 10% forskolin, twice a day (500 mg/day, about 50 mg forskolin), for 12 weeks.[2][3][4]
Is forskolin safe?
Twelve-week trials found no serious problems, but loose stools are common and longer use is unstudied. In mice the whole extract damaged the liver.[1][3][8]
Does forskolin raise testosterone?
One 30-man trial found higher free testosterone after 12 weeks; total testosterone did not change significantly. It has not been repeated.[2]
Can forskolin interact with medications?
In rats it induced liver drug-clearing enzymes and weakened a diabetes drug. Human interaction studies do not exist, so check with a pharmacist if you take prescriptions.[9]
Is Coleus forskohlii the same as forskolin?
Forskolin is the main active compound in the root of Coleus forskohlii; most supplements are root extracts standardized to a percentage of forskolin.[1]
Sources
- [1]Dietary Supplements for Weight Loss: Fact Sheet for Health Professionals (updated May 18, 2022). NIH Office of Dietary Supplements, 2022. fact-sheet
- [2]Body composition and hormonal adaptations associated with forskolin consumption in overweight and obese men.. Obes Res, 2005. RCT
- [3]Effects of coleus forskohlii supplementation on body composition and hematological profiles in mildly overweight women.. J Int Soc Sports Nutr, 2005. RCT
- [4]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. RCT
- [5]The Effectiveness and Safety of Coleus forskohlii Extract as an Anti-Obesity Agent: A Systematic Review.. J Integr Complement Med, 2026. systematic-review
- [6]Forskolin compared with beclomethasone for prevention of asthma attacks: a single-blind clinical trial.. J Int Med Res, 2010. RCT
- [7]Efficacy of forskolin as a promising therapy for chronic olfactory dysfunction post COVID-19.. Eur Arch Otorhinolaryngol, 2024. RCT
- [8]Dietary Coleus forskohlii extract generates dose-related hepatotoxicity in mice.. J Appl Toxicol, 2013. animal-study
- [9]Coleus forskohlii extract attenuates the hypoglycemic effect of tolbutamide in vivo via a hepatic cytochrome P450-mediated mechanism.. Shokuhin Eiseigaku Zasshi, 2014. animal-study
What changed
- First draft. Every PMID checked against NCBI E-utilities esummary (title and year taken from the record) and abstracts read for the cited rows.
- Adversarial review pass: every evidence row re-read against its PubMed abstract; the no-weight-change statements for the 2005 men and 2015 trials come from NIH ODS (May 18, 2022), opened before citing. Industry ties: Sabinsa (ForsLean maker) funding in PMC2129145; Olive Life Sciences supplied capsules in PMC4663611. A 2026 Forcslim trial (PMID 42678522) carries an erratum notice and was kept out. Retraction, expression-of-concern, erratum and withdrawn checks on all 8 PMIDs: none flagged. Page set indexable. Independent browser review (4 parallel reviewers, every evidence row checked against its abstract on the Vercel preview) found: participant count for the 2005 women's trial reconciled to the abstract (23); fixed.