Cocktails consumed at cruising altitude carry potential serious health risks.

When we've had a long day before a flight, we often want to relax during the flight. Some relax by drinking alcohol. While it may seem like a fun way to celebrate the start of a trip, there's one important thing to keep in mind: drinking alcohol on a plane can be really risky. If you're planning on getting some shut-eye on a long-haul flight, you might want to think twice before ordering champagne.

What happens to your body when you are in the air?

When you fly at high altitude, the lower atmospheric pressure means your body gets less oxygen. Normally, blood oxygen levels are around 96% to 100%, but in the sky they can drop to around 90% or even lower.

To adapt, your body goes into overdrive: You start breathing faster to get more oxygen, and your heart pumps faster to get blood circulating throughout your body. This works for most people, but heart disease can make it harder.

Things get even more complicated when you add alcohol to the mix. According to Dr. Matthew Mosquera, a medical expert at McLean Hospital, alcohol can alter the way red blood cells take up oxygen. It disrupts hemoglobin, the molecule responsible for transporting oxygen, making it harder for the body to stay oxygenated.

So, if you already have your boarding pass and drinks order in mind, here are a few things you should keep in mind. There are a few factors that can cause your blood oxygen levels to drop even further on a plane:

AgingAs we age, our bodies become less efficient at adapting to changes in oxygen levels.

Sleeping:Our breathing naturally slows down while we sleep, and this can be even more pronounced on an airplane.

Underlying conditions:If you have lung disease, sleep apnea (when you briefly stop breathing while you sleep), or heart problems, less oxygen will get to your lungs.