1. Judgement by appearance: lock yang is reddish brown in color, and the surface is uneven and wrinkled, and there are particles in the cross-section. The larger the head of the lock yang, the darker the color, the better the quality of the lock yang, the stronger the efficacy, the longer the year.
2. Judge by the shelf life: lock yang in the box has a shelf life instructions, the general shelf life of about two years. If the instructions on the box can not see clearly, you can open the pills to smell, such as pure medicinal fragrance should be in the shelf life or no mold.
The above are two ways to determine the age of lock yang for your reference.