Some tips:
It's easy to say 'they're fine, no harm, etc' but make sure you let her know that you know of the risks. Let her know you've researched it and are aware of all the risks. She'll see through it otherwise. When I told mine, I kept saying 'I'm not keeping anything from you' and basically shocked her with some of the side effects. This lets her know that I'm not a ****ing idiot and I'm aware of this stuff and know how to avoid/minimise it.
Let her know that she's the most important thing and she has the power to make you stop. If she absolutely wants you to, she can tell you to stop and you will. This will force her to be open-minded and educate herself before she thinks about making a decision. Let her know that if she thinks you're getting overly aggressive, you'll stop. But equally tell her not to abuse this power and bring it up in every argument!
Let her know your reasons for taking it and don't let her think it's purely because you're not happy with yourself. Personally, my main reason is for efficiency, I can make more progress with a calculated risk. Obviously none of us are really happy with our bodies, but don't let her know that this is a big reason because it may make her feel like she has a part to play in it.
When you've done all this, point out the dangers of alcohol and, if you've dabbled in reccy drugs together, you can use this too. Not to mention the fact that steroids complement the healthy living lifestyle. You're not shooting up or doing pills every weekend - you're not reckless with your health.
This is what I learnt when I told my girlfriend 1 year into our relationship. We weren't living together (which was my reason for not telling her sooner). I wouldn't say she's fine with it but she understands and once every few weeks I'll speak to her about it and ask her about her thoughts because she is more important to me and I would stop for her. I showed her some websites and instantly she said 'yeah but this is all biased' and it's true... but she trusts me which is worth more. Oh, and the sex drive thing definitely makes it easier for her.
Lastly, be thankful you have such a girlfriend. If she didn't give a **** about you, she wouldn't be making such a fuss. She's not supposed to be fine with you injecting hormones, especially with the way the media has indoctrinated her.
Goodluck!
<message edited by StillBulking on 03 November 2009 22:58>