Look for seals from USP , NSF International , or ConsumerLab to ensure purity and accuracy of ingredients.

Seek labels that state exact standardization, such as 1.8% to 2.2% vitexin or 18-20% oligomeric procyanidins (OPCs) .

High-quality dried berries should be deep red to reddish-brown and firm, with a mildly tart, fruity aroma.

The "best" form depends on your intended use and the speed of results you need: