This item has some anti-radioactive properties, consuming it will lower your radiation level.
Anti-radiation pills are a popular way of lower a player's Radiation level. It is however an uncommon item, this is why players generally choose to use them sparingly.
The pills can be consumed by putting it into the Hotbar and pressing the specified key of 1-6. Or from anywhere in your Inventory by hovering your mouse over the item and then clicking on it with your right-mouse button after which you can select the Consume option.
The pills can be obtained in two different ways: