Why do I feel so much worse after a nap – and how can I avoid it?

Waking up from a nap feeling groggy, tired or ill? Experts say it’s common. Here’s what could be going wrong

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I woke up on the couch feeling nauseous and groggy, with a needle-jabbing-my-temples headache. Was it the flu? Did I eat something bad? There was drool on my cheek, and I glanced at the clock. I remembered checking the time at 1.30 pm; it was now 4pm.

I’d accidentally taken a nap.