Yes, alcohol can dehydrate you.

Dehydration occurs when the body does not have sufficient amounts of fluid to function effectively. This can cause symptoms such as headache, dizziness, and fatigue. Alcohol has a dehydrating effect on the body, especially when a person consumes it in large quantities.

Alcohol is a diuretic.

Diuretics are a type of medication that increases the amount of water and salt that is expelled from the body in urine. Medical professionals use these medications to treat a range of conditions, including high blood pressure and congestive heart failure.

Alcohol causes your body to remove fluids from your blood through your renal system, which includes the kidneysureters, and bladder, at a much quicker rate than other liquids.

If you don’t drink enough water with alcohol, you can become dehydrated quickly.

Why does alcohol dehydrate?

If you drink alcohol with an empty stomach, the alcohol passes directly into your bloodstream. If you’ve eaten before drinking, the rate of alcohol absorption slows down but doesn’t stop.
Once alcohol enters the bloodstream it can travel anywhere in your body. This includes your brain, which is why you feel loopy and your judgment is impaired when you’re buzzed or drunk.
Alcohol enter bloodstream

Why does alcohol dehydrate?

Alcohol is metabolized by the liver, where enzymes break down the alcohol. If you consume an excessive of it, your system becomes saturated, and the additional alcohol will accumulate in the blood and body tissues until it can be metabolized
When its processed by enzymes in the liver, alcohol is converted into a large amount of acetaldehyde. In order to break this substance down and remove it from the body, your liver does most of the work of turning it into acetate.
Alcohol acting as a diuretic
Acetate and other waste products are then removed from the body as carbon dioxide and water, primarily through lungs. Although the kidneys remove waste products, most of the water loss is due to the effect of vasopressin.
BAC measures the ratio of alcohol in the blood. Water is flushed out much faster than alcohol is processed. This can increase your BAC significantly if you don’t replenish your body’s supply with a few sips of water as you drink.If you consume more alcohol while your body is still processing your previous drinks, your BAC can rise quickly.