You can heat it in a microwave to reverse the crystallization.

Do not do this ifs the honey is in a squeezable bear container. The honey will boil, make a hole in the bear and spray honey all over the inside of your microwave (the turntable helps this). This will make a huge mess and will make opening the microwave more challenging.

I think the general recommendation is to put the bottle in warm/hot water. I don’t believe microwaving is a good idea, unless done at low power for longer.

Sous-vide at 110F. It will take hours, but it won't affect the flavor.

Warm water is sufficient, though with recent cautions about heating plastics and leaching of chemicals, I'd prefer transferring the honey to a glass jar if it's not packaged in such already.

You can double-boil if you want, where the jar sits in a shallow water bath which you boil for 10--20 minutes or so to decrystalise the honey.

The first thing that popped into my head after reading this was the large container of Kirkland honey I have.

I thought: “Costco wouldn’t lie to me? Would they?”

Now I must go and find out.

Just because they're not lying doesn't mean they've done the work of finding out whether the honey is pure.

Costco apparently sells one of the few olive oils that aren't adulterated. So their honey might also be real.

Crystallization isn’t an indicator of fake or low quality honey.

We have had wildflower honey crystallize in the honeycomb when we left it in the garage over winter.

It can be decrystallized easily with gentle heat. I put our jars in a water bath in a pot and leave it over a low setting for about an hour until it is good. The water never gets over 125 or so, which should be fine.

I had meant the other way, that it crystallizes so if it means that it’s a good honey.

There are a number of things that can affect crystallization; Storage conditions, filtering, what the bees foraged, etc.

There are some genuine honeys which rarely crystalize.

Afaik (as an amateur beekeeper), it is not a good indicator of anything in particular, there are even reports of adulterated honey crystallizing. This make sense, since honey and fake honey are both a supersaturated solution of sugars that will gladly crystalize if given an opportunity.