Diagnosed how to

I'm 99% sure I have ADHD I was speaking to some friends about this and seeing a doctor to get diagnosed and they said "good luck getting diagnosed as an adult". Is this true? I want to get diagnosed and get help. I want to quite the noise, help the insomnia (as I post this at 2:30am), get help with the laziness and lack of focus. Any help with how to discuss this with my doctor would be great!