Can I add items to my next order with an existing Subscribe & Gain™ order?

Yes! 

To do so, you must be logged into your Bodybuilding.com account. Visit the item’s page you wish to add to your order, and find the "Add this to my order on:" button. When you click this button, you will have the option to add the item as a one-time only add-on to your next order or as a recurring subscription item.