What kind of machine do you have? Look in the book that came with your machine and it will tell you what to use. Certain mchines take certain thread to be happy and preform well. Suzanne

My thread supplier tells me that Janomes require cotton bobbin thread, so yes, you'd need to check what your brand is fond of.

This happened me last week and I used embroidery thread in the bobbin until I could get to the shop to get more, and the embroidery thread worked out fine!

They do sell bobbin thread if you wanted to have some on hand for the future. I'd use regular embroidery thread in the meantime.

My quilt/embroidery shop told me it didnt matter what you used. The only difference was the back side of the embroidery would be heavier then if you used the lighter bobbin thread. At the time I was using my embroidery thread as top and bobbin thread. But some machines might be not work with it, they can be a bit picky when they want to.

Embroidery thread in the bobbin only if you want your work to be seen from the back as well.
Ordinary overlock polyester (nice big cone) works fab as unseen bobbin thread.
I wind my own bobbins with this thread and use it all the time.
From Bev