You've known since you were a kid that when you're sick, you need to get as many fluids in as possible. This is because, as Indiana Public Media explains, you're losing more fluids than normal through a runny nose, sweating, vomiting, and diarrhea. It goes further than this, though. If you have a fever, you might be even more dehydrated, because even the slightest rise in your body temperature could mean an increased metabolism. Your body is working faster and harder, which means it needs more water and more oxygen. This is why it's so crucial to stay hydrated when you're sick.
Now, what about alcohol?
Alcohol also dehydrates you, because it's a diuretic — meaning it makes your body produce more urine than normal. LiveStrong explains this happens because alcohol prevents the release of antidiuretic hormone (ADH), which is necessary for water reabsorption. So, instead of your kidneys completing this task, that water is eliminated from your body as urine.
To review: being sick makes you dehydrated. Drinking alcohol makes you dehydrated. The effects of dehydration could range from dizziness and confusion (per the Centers for Disease Control and Prevention) to death.
Takeaway: don't imbibe when you're sick.
