Dunham created the hit HBO series in 2012 and plays lead character Hannah, so going from such a fast-paced working environment to being housebound does not sit well with the star.
"That's a hard thing to do, but I'm trying, because all I want is to make season 6 of Girls the best one yet," she wrote.
"I'm lucky enough to have support and backup from (producers) Jenni (Jennifer Konner), Judd (Apatow) and the whole Girls gang. So many women with this disease literally don't have the option of time off and I won't take it for granted. Wishing you all health & happiness, in whatever form suits you. Back soon xxLena."
Lena first opened up about her battle with the condition in November via her weekly newsletter, Lenny Letter.
Girls screens on SoHo in New Zealand.
- WENN