Coleus forskohlii is a tropical plant in the mint family, now formally known as Plectranthus barbatus, that grows across Asia. It has been used for centuries in Ayurvedic medicine under the name Makandi. The plant’s claim to modern fame is a single compound found in its roots called forskolin, which has attracted attention for its potential effects on body composition, eye pressure, and hormone levels.
How Forskolin Works in the Body
Forskolin is a naturally occurring diterpene, a type of chemical compound produced by the plant’s roots. What makes it unusual is its ability to directly activate an enzyme that increases levels of a cellular messenger called cAMP (cyclic adenosine monophosphate). cAMP is a signaling molecule involved in dozens of bodily processes: it tells cells to release stored fat, relaxes smooth muscle in the airways, and influences hormone production.
Most supplements and clinical trials use a standardized root extract containing 10% forskolin. The typical study dose is 250 mg of this extract taken twice daily, delivering about 50 mg of forskolin per day. You’ll find it sold as capsules, sometimes labeled under the older botanical name Coleus forskohlii and sometimes as forskolin extract.
Effects on Body Composition
Forskolin’s most popular use is as a weight loss supplement, and there is some clinical evidence behind this. A review identified seven human studies, four of which were randomized, double-blind, and placebo-controlled. Across these trials, people taking the extract showed significant differences in body weight change compared to those on a placebo, with a meaningful reduction in body fat.
One well-known 12-week trial in overweight and obese men found that 250 mg of 10% forskolin extract taken twice daily favorably altered body composition while also increasing bone mass. The effects were modest, not dramatic, but they were statistically significant compared to placebo. The proposed mechanism ties back to cAMP: higher cAMP levels promote the breakdown of stored fat for energy, a process called lipolysis.
Testosterone and Hormonal Effects
That same 12-week trial in 30 overweight men produced an interesting secondary finding. Men in the forskolin group had significantly higher serum free testosterone levels compared to those taking a placebo. Total testosterone trended upward by about 17% in the forskolin group, while the placebo group saw a slight decline, though the total testosterone difference didn’t reach statistical significance on its own.
Free testosterone is the portion that’s biologically active and available for the body to use, so even a modest increase could be relevant. Still, this comes from a single small study with 15 people per group. The result is promising but far from settled.
Eye Pressure and Glaucoma
Forskolin can also be applied directly to the eyes. In one open-label study of 90 adults with open-angle glaucoma (eye pressure above 24 mmHg), 1% forskolin eye drops used three times daily for four weeks reduced intraocular pressure by an average of 4.5 to 5.4 mmHg. That’s a clinically meaningful drop for people managing glaucoma.
This application is particularly interesting for people who have both glaucoma and asthma, since the standard glaucoma treatment (beta-blocker eye drops) can worsen breathing problems. Forskolin eye drops may offer an alternative that avoids that conflict. These are not widely available over the counter, though, and would need to be discussed with an eye care provider.
Respiratory Uses
Because cAMP relaxes smooth muscle, forskolin has bronchodilating properties. It can open up the airways in a similar way to some asthma medications. Oral forskolin has been studied at 10 mg daily over periods of two to six months for asthma, though the research base here is thin compared to its body composition studies.
Safety and Drug Interactions
Forskolin has not been thoroughly studied for long-term safety, and no optimal dose has been officially established. The clinical trials that exist generally report it as well tolerated at standard doses, but several important cautions apply.
The most serious concern is forskolin’s interaction with blood-thinning medications like warfarin and heparin, as well as clot-dissolving drugs. It may amplify their effects, increasing bleeding risk. The same applies to common anti-inflammatory drugs like ibuprofen, aspirin, and naproxen.
Forskolin can also lower blood pressure. If you’re already taking medication for high blood pressure, adding forskolin could push your levels too low. Similarly, it may enhance the effects of blood sugar-lowering medications like metformin or glipizide, creating a risk of hypoglycemia.
People with the following conditions should be especially cautious:
- Heart problems, since cAMP affects heart rate and contractility
- Stomach ulcers, as forskolin may increase stomach acid
- Polycystic kidney disease, where forskolin is specifically contraindicated
- Diabetes, due to potential blood sugar interactions
- Depression, though the mechanism here is less well defined
Safety during pregnancy and breastfeeding is unknown, so it’s best avoided in those situations. One practical concern worth noting: because forskolin is sold as a dietary supplement, the actual forskolin content can vary significantly between brands. Third-party tested products offer more reliability on what you’re actually getting.