Use it when something is about to fail or end very soon, not just facing problems.

Imminent Failure

It's informal and might be used among friends or in relaxed settings, not in formal writing or speech.

Casual Tone

The phrase is British slang, so it's more familiar to UK speakers than to other English speakers.

Used to describe someone's health being in a critical state, implying close to death.

Be careful with usage as it refers to death or terminal conditions, which can be sensitive topics.

It's an idiom, so it may not mean literal death but a figurative end to something.