This was posted in another thread, it might help you.

"Not me, but there's a guy on BaldTruthTalk that went from a NW5A/NW6 down to a diffuse NW2/NW3 in 12 months of microneedling with a 1.5mm dermaroller with minoxidil twice daily, including microneedling days. Take a look at these pictures: http://imgur.com/gallery/DW6yl There's greek guy in his 40s who seems to be quite thin on the scalp, and then went to a full head of hair. He used a 2mm dermapen, and not a 1.5mm dermaroller. 2mm is a bit deep, and I read somewhere that 1mm dermapen should be fine. Dermarollers don't often penetrate deep enough, where as dermapens do. He didn't use minoxidil, but instead opted for a bunch of supplements. Here: http://imagizer.imageshack.us/v2/1024x768q90/633/L8SirE.jpg Here's the greek thread: http://www.hairlossgr.com/threads/wounding-dermapen-%CF%84%CE%BF%CF%80%CE%B9%CE%BA%CE%AC-%CE%BA%CE%B1%CE%B9-%CF%83%CF%85%CE%BC%CF%80%CE%BB%CE%B7%CF%81%CF%8E%CE%BC%CE%B1%CF%84%CE%B1.10640/ There's another guy in the same BaldTruthTalk thread who managed to get back his hairline: https://www.baldtruthtalk.com/threads/13420-Dermarolling-Community-Trial?p=241714&highlight=#post241714 However, I have to leave an obligatory "take everything with a grain of salt" disclaimer. Just as mentioned here, not everyone could see results coming out of this regiment. Here's an advice: if you are microneedling, do not apply any anti-inflammatories (Nizoral/Regenepure DR/ketoconazole) within the first 3-5 days after microneedling. The purpose of microneedling is to upregulate PGE2 inflammation, and downregulate PGD2. PGE2 has been known to induce hair growth, where as PGD2 has been known to do the opposite. After 3-5 days, the PGE2 and PGD2 levels should go back to baseline, and you should be able to recommence the application of anti-inflammatories."

Generally 1.5mm once a week I've seen as the norm.