Olive Leaf Benefits, Side Effects and Dosage

Olive leaf extract is a supplement made from the leaves of the olive tree. It’s rich in polyphenols, especially oleuropein, that have antioxidant and anti-inflammatory properties. Human research suggests olive leaf may help lower blood pressure, support healthy blood sugar, and possibly improve cholesterol and other cardiovascular risk factors. Common supplemental amounts range from about 500 to 1,000 mg of olive leaf extract per day, although the amount of oleuropein may matter more than the total extract weight. Side effects are usually mild, but olive leaf may interact with blood pressure and diabetes medications.

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The olive tree is best known for giving us olives and olive oil, two staples of the Mediterranean diet. But the leaves of the same tree have also been used in traditional medicine for centuries.

Today, olive leaf is commonly sold as a tea, liquid extract, powder, or capsule. Much of the interest centers on a natural compound called oleuropein, although olive leaves contain several other potentially useful polyphenols.

Research on olive leaf isn’t as extensive as research on olive oil. Still, there’s enough human evidence to make it more than just another herbal supplement with impressive claims and little data behind it. Its possible effects on blood pressure and metabolic health are especially interesting.

What Is Olive Leaf Extract?

Olive leaf extract comes from the leaves of Olea europaea, the same tree that produces olives. The leaves naturally contain several plant compounds, including oleuropein, hydroxytyrosol, flavonoids, and other phenolic compounds.

Oleuropein usually gets the most attention. It has antioxidant activity and appears to influence inflammation, blood vessel function, and glucose metabolism.

These compounds help explain why olive leaf is often discussed alongside other foods and antioxidant supplements. However, having antioxidant activity in a laboratory doesn’t automatically mean a supplement will prevent disease in humans. That’s an important distinction with olive leaf, as it is with many plant extracts.

Fortunately, researchers have conducted several human trials, so we have something more useful to work with.

Olive Leaf May Help Lower Blood Pressure

Blood pressure support is probably the most convincing potential benefit of olive leaf extract. A 2017 randomized controlled trial involving 60 pre-hypertensive men found that a phenolic-rich olive leaf extract lowered both systolic and diastolic blood pressure compared with a control. Participants consumed an extract providing 136 mg of oleuropein and 6 mg of hydroxytyrosol each day for six weeks (1).

More recently, a much larger randomized trial involving 621 people treated for hypertension also reported favorable results. After 12 weeks, olive leaf extract produced a greater reduction in 24-hour systolic blood pressure than placebo. Researchers also observed improvements in several metabolic markers (2).

A 2025 systematic review and meta-analysis reached a similar general conclusion, suggesting olive leaf may reduce blood pressure in people with prehypertension or hypertension (3). That’s encouraging, but olive leaf shouldn’t be viewed as a replacement for prescribed medication. If anything, it may have a role as an additional lifestyle or nutritional strategy.

You can also read our guide to the best supplements for high blood pressure for a broader look at the subject.

It May Support Healthy Cholesterol Levels

Some research suggests olive leaf could also have modest benefits for cholesterol and triglycerides. In the six-week study mentioned above, olive leaf supplementation reduced total cholesterol, LDL cholesterol, and triglycerides compared with the control treatment (1). Another trial involving olive leaf tea found reductions in LDL cholesterol among adults with prediabetes (4).

On the other hand, the evidence isn’t completely consistent. An eight-week randomized trial involving 77 overweight or obese adults with mildly elevated cholesterol found no significant improvement in cholesterol, triglycerides, blood pressure, glucose, or insulin compared with placebo (5).

That conflicting result is worth paying attention to. Supplement research often produces a messy picture, and olive leaf is no exception.

Differences in the extracts, oleuropein concentrations, participants, diets, and treatment periods could help explain the mixed findings. For now, olive leaf appears promising for cardiovascular health, but it isn’t a substitute for proven approaches to managing high cholesterol. Our guide to supplements for heart and cardiovascular health discusses several other options.

Olive Leaf May Improve Insulin Sensitivity

Olive leaf may also influence how your body responds to insulin. In a randomized crossover study, 46 overweight middle-aged men received olive leaf polyphenols or a placebo for 12 weeks. The supplement provided 51.1 mg of oleuropein and 9.7 mg of hydroxytyrosol per day.

Compared with placebo, olive leaf supplementation improved insulin sensitivity by about 15% and pancreatic beta-cell responsiveness by about 28% (6). Those beta cells are important because they produce insulin.

However, newer research has added some uncertainty. A small 2025 pilot study in adults with type 2 diabetes found that olive leaf extract was well tolerated but didn’t produce a statistically significant improvement in HbA1c compared with placebo (7).

So, olive leaf might influence glucose metabolism, but we shouldn’t jump from that to saying it treats diabetes. The clinical evidence simply isn’t strong enough yet. Anyone interested in this area may also find our article on supplements to lower blood sugar helpful.

Olive Leaf Has Antioxidant and Anti-Inflammatory Properties

Oleuropein, hydroxytyrosol, and related olive polyphenols can help neutralize reactive molecules known as free radicals. When free-radical production overwhelms the body’s antioxidant defenses, oxidative stress can occur.

Researchers have linked long-term oxidative stress with cardiovascular disease, metabolic disorders, and many of the biological changes associated with aging. Olive polyphenols may help strengthen the body’s defenses against this process.

Olive leaf compounds also appear to affect inflammatory pathways. Some human research has reported changes in inflammatory markers, although the results aren’t consistent across every study (1,3).

If you’d like more background on why these plant compounds receive so much attention, see our guide to polyphenols and their health effects.

What About Olive Leaf for Immune Support?

You’ll often see olive leaf promoted as a “natural antiviral” or antimicrobial supplement. There is some scientific basis behind the claim. Oleuropein and other olive compounds have demonstrated antimicrobial activity in laboratory experiments. Researchers have studied them against certain bacteria, fungi, and viruses.

The catch is that laboratory activity doesn’t necessarily translate into meaningful infection-fighting effects when someone swallows an olive leaf capsule.

At this point, there isn’t enough good human evidence to recommend olive leaf as a treatment for viral or bacterial infections. Think of its antimicrobial properties as an interesting area of research rather than a reason to replace conventional treatment.

Olive Leaf Extract Dosage

There is no officially established daily dosage for olive leaf extract. Human studies have used different extracts and concentrations, making simple comparisons difficult. Some trials have used around 500 mg per day, while others have studied approximately 1,000 mg per day (3,5).

The number on the front of the bottle doesn’t tell the whole story, though. A 500 mg extract standardized to 20% oleuropein provides about 100 mg of oleuropein. Another 500 mg product containing 10% provides only about 50 mg. That’s a substantial difference even though both bottles say “500 mg olive leaf extract.”

Clinical studies have also used specific amounts of olive polyphenols rather than simply measuring the total weight of the leaf extract. For example, one study provided 51.1 mg of oleuropein daily, while another provided 136 mg (1,6).

For general supplementation, following the manufacturer’s recommended serving is sensible. Starting toward the lower end may also help you judge how well you tolerate it.

Olive Leaf Side Effects

Olive leaf extract appears to be reasonably well tolerated in human studies. The large 2025 hypertension trial reported no significant adverse events, while a recent diabetes trial also found the supplement to be generally well tolerated (2,7).

Still, supplements can affect people differently. Possible side effects may include:

Stomach discomfort
Nausea
Diarrhea
Headache
Dizziness
Allergic reactions in sensitive individuals

There’s another practical concern. Because olive leaf may lower blood pressure, combining it with blood pressure medication could potentially cause your pressure to fall too low. Symptoms might include dizziness, weakness, or feeling faint.

The same basic caution applies to diabetes medication. If olive leaf improves insulin sensitivity or lowers blood glucose in some people, combining it with glucose-lowering drugs could theoretically increase the risk of excessively low blood sugar.

Pregnant or breastfeeding women should generally avoid concentrated olive leaf supplements unless their healthcare provider approves them because safety data are limited.

How to Choose an Olive Leaf Supplement

When comparing products, don’t look only at the milligrams of olive leaf extract. Check whether the manufacturer tells you how much oleuropein the product contains.

A standardized extract makes comparison much easier. You might see labels listing 10%, 20%, or even higher concentrations of oleuropein.

Third-party testing is another plus. Herbal supplements can vary considerably in purity and potency, so buying from a manufacturer that tests for contaminants and verifies ingredient levels gives you a little more confidence that you’re getting what the label promises.

Olive leaf tea is another option, although its concentration is less predictable than a standardized capsule.

The Bottom Line

Olive leaf has moved beyond its traditional-medicine roots and now has a respectable, though still developing, body of human research behind it. The strongest evidence appears to involve blood pressure and cardiovascular health.

There are also intriguing findings involving insulin sensitivity, blood sugar, cholesterol, inflammation, and oxidative stress. At the same time, several studies have produced neutral results, so olive leaf shouldn’t be treated as a cure-all.

For most healthy adults, a standardized olive leaf extract used according to label directions appears reasonably well tolerated. Pay attention to the oleuropein content rather than relying solely on the total milligrams of extract.

And if you’re taking medication for hypertension or diabetes, it’s worth talking with your healthcare provider before adding olive leaf. In those situations, the supplement’s potential benefits are also the reason some extra caution makes sense.

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