Several supplements have good evidence for lowering cortisol, with ashwagandha, phosphatidylserine, and rhodiola rosea showing the most consistent results in clinical trials. The effects aren’t instant. Most studies measure significant cortisol reductions after 4 to 12 weeks of daily use, so consistency matters more than any single dose.
Ashwagandha
Ashwagandha is the most widely studied supplement for cortisol reduction. Clinical trials consistently show it lowers serum cortisol compared to placebo, and an international taskforce has provisionally recommended 300 to 600 mg of root extract daily for generalized anxiety, a condition closely tied to elevated cortisol. One randomized controlled trial in 60 adults found reduced cortisol levels after 8 weeks of taking either 250 or 600 mg of extract daily, while the placebo group saw no meaningful change.
The benefits appear to be greater at doses of 500 to 600 mg per day than at lower doses, based on multiple trials reviewed by the National Institutes of Health. Across studies, doses ranged from 240 to 1,250 mg per day of extract. When shopping for ashwagandha, look for products standardized to a specific percentage of withanolides, the active compounds. Most well-studied formulations are standardized to between 1.5% and 5% withanolides.
Phosphatidylserine
Phosphatidylserine (PS) is a fat-like molecule found in cell membranes, and it appears to directly blunt the hormonal cascade that triggers cortisol release. It’s particularly effective at reducing cortisol spikes caused by physical or mental stress rather than lowering your baseline level throughout the day.
In a double-blind, placebo-controlled study of eleven intensely trained athletes, 800 mg of PS daily reduced the cortisol rise by 20% compared to placebo. A separate study in nine nonathletic men found a dose-dependent effect: 400 mg daily reduced post-exercise cortisol by 16%, and 800 mg daily reduced it by 30%. If your cortisol issues are tied to intense training or physical stress, PS is one of the better-supported options. Most studies use 400 to 800 mg per day.
Rhodiola Rosea
Rhodiola rosea is an adaptogenic herb that targets the cortisol awakening response, the natural spike in cortisol your body produces when you wake up. In people dealing with chronic stress or burnout, this morning spike is often exaggerated, leaving you feeling wired and anxious before the day even starts.
A study published through the American Botanical Council found that 576 mg per day of a standardized rhodiola extract significantly reduced the cortisol awakening response after 28 days compared to placebo. That relatively quick timeline makes rhodiola worth considering if you’re looking for something that works within the first month. Typical doses in research range from about 400 to 600 mg daily.
Vitamin C
High-dose vitamin C can lower cortisol, but “high-dose” is the key detail. In a study of ultramarathon runners, 1,500 mg per day taken for seven days before and two days after the race significantly lowered post-race cortisol levels. The group taking 500 mg per day showed no meaningful difference from placebo. So if you’re going to try vitamin C for cortisol, you likely need at least 1,000 to 1,500 mg daily. Below that threshold, the effect disappears.
This is most relevant if your cortisol spikes are driven by intense physical activity. The evidence for vitamin C lowering resting cortisol in sedentary or moderately active people is much thinner.
Omega-3 Fatty Acids
Fish oil may help lower morning cortisol levels over time. A study in adolescents found that omega-3 supplementation reduced morning cortisol at 12 weeks compared to baseline, while an omega-6 control group showed no change. The effect was modest, and omega-3s are better thought of as a supporting player rather than a primary cortisol-lowering tool. That said, omega-3s carry broad benefits for inflammation and mood, so they’re a reasonable addition to a cortisol-focused supplement stack.
How Long Before You See Results
Don’t expect overnight changes. The fastest-acting option in the research is rhodiola rosea, which showed significant effects at 28 days. Ashwagandha trials typically measure results at the 8-week mark. Omega-3s took 12 weeks. Phosphatidylserine works differently because it blunts acute cortisol spikes rather than changing your baseline, so you may notice effects on workout recovery or stress responses sooner.
If you’re combining supplements with lifestyle changes like better sleep, regular moderate exercise, and reduced caffeine intake, the timeline may compress. Chronically poor sleep alone can raise cortisol by a significant margin, so no supplement will fully compensate for sleeping five hours a night.
Picking the Right Option for Your Situation
Your best choice depends on what’s driving your cortisol up:
- General chronic stress or anxiety: Ashwagandha at 300 to 600 mg daily is the most broadly supported option.
- Exercise-induced cortisol spikes: Phosphatidylserine at 400 to 800 mg daily has the strongest evidence for blunting cortisol after physical stress.
- Morning anxiety or burnout: Rhodiola rosea at 400 to 600 mg daily specifically targets the cortisol awakening response.
- Heavy training loads: Vitamin C at 1,500 mg daily can reduce cortisol around intense endurance exercise.
- Broad support: Omega-3 fatty acids won’t dramatically drop cortisol on their own but contribute to a lower-stress hormonal environment over months.
These supplements can be combined, and many people stack ashwagandha with phosphatidylserine or omega-3s. Start with one, give it at least four to six weeks, and track how you feel before adding another. That way you’ll know what’s actually working.