Overview
Oolong (also spelled wulong) is a Camellia sinensis tea that sits between green and black tea on the oxidation spectrum — roughly 10% to 80% oxidized, depending on style. This wide range gives oolong the most diverse flavor profile of any tea category, from light and floral (Tie Guan Yin / “Iron Goddess,” lightly oxidized) to dark and roasted (Da Hong Pao / “Big Red Robe,” heavily oxidized and roasted). Most oolongs are grown in Fujian province, China, or Taiwan, and processing typically involves withering, bruising/shaking the leaf edges, partial oxidation, “kill-green” heating to halt oxidation, rolling, and drying.
Active compounds and evidence
Because oxidation is partial, oolong’s catechin and theaflavin content — and its caffeine content — generally falls between green and black tea, though this varies considerably by specific processing. Caffeine per cup is typically in the 30–50 mg range. As with other true teas, oolong contributes polyphenols associated in observational research with modest cardiovascular benefit; a small number of trials have also looked at oolong and metabolic markers (e.g., fat oxidation, glucose handling), with mixed and generally modest results that don’t support strong weight-management claims sometimes made in marketing.
Safety and contraindications
- Caffeine content is variable: Because oxidation level and steeping practice vary widely by style, caffeine content is less predictable than for green or black tea; caffeine-sensitive individuals should treat any oolong as a moderate-caffeine beverage until they know a specific tea’s strength.
- Iron absorption: Like other true teas, oolong’s tannins can modestly reduce non-heme iron absorption if consumed with iron-rich meals.
- Pregnancy: Count oolong’s caffeine toward the general pregnancy guidance of roughly 200 mg/day.
How it’s typically prepared
Traditionally brewed gong fu style — a high leaf-to-water ratio in a small teapot or gaiwan, with short (30-second to 1-minute) steeps repeated multiple times, allowing the flavor to evolve across infusions.
Sources
Clinically reviewed by Dr. Shilpa Thakur. Last reviewed 2026-07-20. Educational information, not medical advice; consult a qualified clinician about caffeine intake if pregnant, breastfeeding, or caffeine-sensitive.