Stinging nettle leaf extract concentrates the plant into a form standardized for flavonoids or scopoletin. People take it in capsules or tablets for joint discomfort and seasonal allergies. Taking it with food can reduce the chance of stomach upset.
The extract has both anti-inflammatory and antihistamine activity. It can affect blood pressure, blood sugar, and urination. Those on blood pressure medications, diuretics, diabetes medications, or blood thinners such as warfarin should use caution because interactions are possible.