Is Kaioken + Ultra Instinct possible?

[Doctor.]

I mean, theoretically? It should be, both in the anime and the manga. UI is all about maintaining composure and allowing your body to fight on its own and efficiently. He could burst into Kaioken to maximize speed and power. Ultra Instinct itself already strains Goku, so it's not like Kaioken's strain by itself would pop him out of the form. The two forms together may be a bit too much, but perhaps to someone like Beerus or Whis, who don't need to "transform" to use UI, it would be feasible.

[theherodjl]

When DBS sets up another arc, Goku will probably be mixing SSJ with UI to combat SSJ3/SSJG/SSJB Kefla & Ultra-Justice Jiren so why not???

[CTAkuma]

Yes, he can theoretically use it in every form unless stated otherwise.

[Lionel]

Is it the body's instinct to project a self-harming technique that stresses itself to the point of ripping apart your own muscles. From a first glance it doesn't seem like this would be prudent for the survival of the body. Knowing how the series likes to employ sensationalism, it wouldn't surprise me if this were devised somewhere down the line.

Could it happen? Yeah, but I expect it would probably be some kind of last resort manoeuvre as a sort of flight or fight reaction. That probably won't be the case in the actual product.

[Xeztin]

In the manga, I don't know. Ultra Instinct seems to be hard enough to hold at this point in time on its own, he'd probably have to go through mental trianing to learn to feel or think of nothing while balancing that power up on top of it. I was curious of this and how SSJ would work with it.

[Mister_Popo]

Theoretically he should be able to use Kaioken in all states.
If he would truely master UI, being able to control and use it in such a way it doesn't cause massive strain on his body, maybe it would be better manageable to combine it with Kaioken, if it were possible in the first place.
If he had tried that during TOP, i reckon he would have been toast instantly.

On the other hand, UI should refer to a state that is beyond every normal power-up available, beyond the ultimate limit that's supposed to be full power Blue + 20 times Kaioken.
From that perspective the idea to combine UI with other forms or techniques may be somehow debatable.