how do i know if a friend is addicted to meth?

a friend of mine has started lying to me a lot- he told me that he couldn’t pick me up from the airport becasue he had small pox.. i asked q&a users about the disease and apparently it’s been gone since the 70s. he just text messaged me and asked for 2,000.00 for a dr visit. my neighbor says it sounds like a meth addiction.

how do i know?
how do i help?
my neigbors brother was addicted for 4 years, i told him other stuff – like he lost 60 pounds in 2 months, how he calls me at 3 am, and sometimes he ( my friend ) is really moody- he is in a good mood then he yells at me for nothing.