round green tablet
with capital letters, LSP
Based on the description provided, I found your pill to be Lisinopril (40 mg).
NOTE: I also located conflicting info that this pill is gray and not green as you mentioned. You may want to double check your pill for verification of this.
Lisinopril is used to control and lower high blood pressure.
For more information about this drug, please refer to the link below...
If you have any more questions or concerns, please post back and I will be happy to help you.