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Drinking on an empty stomach, and other factors that can affect your BAC

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Most estimates of Blood Alcohol Content (BAC) assume you are drinking with food in your stomach. If you drink on an empty stomach, this can affect your BAC, but why?

How does drinking on an empty stomach affect BAC?

When you have food in your stomach, the food will absorb the alcohol and hold it in the stomach for a while while the food digests. While the food is being digested, the valve connecting the stomach to the intestines stays closed, keeping the alcohol in the stomach longer. About 80% of alcohol is absorbed in the intestines, and when it’s held in the stomach, this delays the speed of the alcohol absorption. So, when there is food in your stomach, the alcohol enters the bloodstream more slowly, with some estimates of up to 75% slower. While this factor doesn’t necessarily affect the overall amount of alcohol that would be absorbed eventually, if you drink on an empty stomach, BAC can increase more quickly.

However, drinking on an empty stomach does actually affect the total amount of alcohol that will be absorbed into your bloodstream, as well. Your stomach has gastric enzymes that break down a portion of the alcohol that you consume. However, this only happens if you have food in your stomach to hold the alcohol there long enough to be metabolized in the stomach. If the stomach is empty, the alcohol flows quickly through the stomach, so very little is broken down by those gastric enzymes. This leads to a higher total amount of alcohol that is able to be absorbed into the bloodstream by the intestines, leading to a higher BAC overall.

In fact, in one example we calculated, having just two drinks could lead to a BAC of .03 if eating while drinking, but .05 if the stomach was empty, and .05 is sufficient for a DWAI arrest. (These numbers are dependent on the person’s weight, type of drink, and duration of drinking, of course.) Some researchers estimate that BAC can be 2 – 3 times higher if drinking on an empty stomach.

What other factors could affect BAC?

As we talked about in a previous post, gender can also affect BAC. There are other factors that may also affect your BAC, but there is limited research on them, so the impact on BAC is less certain. These potential factors include cigarette smoking, being on a keto diet, being diabetic, and drinking carbonated beverages.

Smoking may affect BAC

There is some evidence that smoking cigarettes could affect your Blood Alcohol Content (BAC). Smoking may lead to alcohol staying in the stomach longer, leading to slower absorption of alcohol into the blood. If this is the case, stomach enzymes would have more opportunity to break down the alcohol before it is ever absorbed, leading to a lower BAC.

However, smoking nicotine could also contribute to higher measurements of an alcohol metabolite (acetaldehyde) in the lungs, so this could falsely cause higher BAC readings in smokers when tested with a Breathalyzer. The presence of acetaldehyde typically suggests that you have consumed alcohol, but some research suggests that smokers could have higher concentrations of acetaldehyde in the lungs even in entirely sober people. Therefore, BAC readings in smokers could be higher with breath tests than blood tests.

Keto diets, being diabetic, and drinking carbonated beverages could affect BAC Consuming a lower proportion of carbohydrates in your diet, such as with a Keto diet, can lead to low blood glucose levels. Small amounts of consumed alcohol can stop the production of glucose, also lowering blood glucose levels. This could indirectly affect breathalyzer results, so could result in inaccurate BAC results. Having diabetes may possibly also affect breathalyzer results as well. Furthermore, at least one researcher suggests that drinking carbonated beverages may help alcohol to be absorbed more easily, leading to a higher BAC.

What DOESN’T affect your BAC?

Contrary to common folklore, sucking on a penny before a breathalyzer does not lower your BAC results. Drinking coffee also does not help you to “sober up”. Coffee contains caffeine, a stimulant drug, but this does not actually counter or negate the effects of alcohol, and does not change the amount of alcohol present in your blood, so will not lower your BAC.

The best way to not have to worry about your BAC is to always have a designated driver when you drink. If you are charged with driving while intoxicated in Colorado, contact attorney Kevin Churchill for a free consultation. He has been representing those charged with DUI and DWAI in the Front Range for over 24 years.