I don't know first hand but I did find this return policy for you
GNC will gladly refund or exchange products within the following guidelines:
Valid sales receipt accompanied by product (used or unused) guarantee and the label states, "Money Back Guarantee."
Products returned without a receipt may be exchanged for a product of equal or greater value with customer paying the difference.
Credit Card Purchases:
Credit will be issued to the Charge Account when accompanied by product bottle (used or unused).
A refund is issued after a 7-day waiting period.
* Gift Certificates
* Phone In Option
* Free Nutrition Information
Gold Card Discount Club
Accepted Payment Methods
* American Express
* ATM/Debit Cards
* Personal Check
* GNC Gift Certificates
The Shops at Willow Bend Gift Certificates
Hope this was somewhat helpful ~~~