I am about to paint my bathroom ceiling which is highly prone to mildew/mold. Can I mix a bit of bleach with my paint to help the ceiling resist the mildew? I am using a high gloss latex.

No, don't mix bleach into your paint.

What you should do is clean the mildew off the ceiling with bleach, rinse that bleach off afterwards with clean water, and then paint the bathroom ceiling (and walls) with a paint made specifically for bathrooms, like Zinsser PermaWhite Bathroom Paint (available at Home Depot and other fine stores).

Zinsser Permawhite has a mildewcide in it. That mildewcide is so highly soluble in water that even the high humidity on one side of the paint will cause the mildewcide in that paint to migrate to the humid side of the paint where it kills any mildew spores that land on the paint before they have a chance to grow. The mildewcide is a solid dissolved in the latex paint. It is not a liquid that can evaporate. So, because of the high solubility of this mildewcide in water, it's best not to clean the bathroom walls with water any more often than is necessary. Doing so will remove the mildewcide from the surface of the paint. That will cause more mildewcide to migrate to the surface, reducing the time the paint is resistant to mildew. Once the reserve of mildewcide in the paint has been depleted, Zinsser's PermaWhite Bathroom paint will be no more mildew resistant than any other latex paint.

I own a small apartment block, and I use Zinsser's PermaWhite Bathroom paint in all 22 of my bathrooms, and none of them have any mildew growing on the paint. Zinsser's guarantees their PermaWhite Bathroom paint to remain mildew free for 5 years, but my experience is that if it only remains mildew free for 5 years, you got a bad can of paint. Typically, after applying two coats of paint (to double the reserve of mildewcide), this paint will remain mildew free for well over 15 years.

Hope this helps.

Thank you Nestor. I am going to visit Home Depot and get the Zinsser PermaWhite Bathroom paint. Sounds great. I really appreciate the advice. Thanks again.

It's a tintable white, so you can tint it to any off white or pastel colour. And it comes in satin and semi-gloss.

It's a very good product.

Sherwin Williams also makes a similar product simply called "Bath Paint".

Just to add: Put in (if you don't have one) and USE an exhaust fan that is vented to the outdoors during every bath and shower. Put a timer on the switch so it runs for at least 15 minutes afterward too.

The mold/mildew needs moisture to grow.