I am a lightweight. When am I safe to drive?

April 21, 2017 8:22 PM

I'm 6'2", 180 lbs. After one beer I'm feeling pretty good. A few months ago, a half of a beer on an empty stomach made me very intoxicated. I avoid craft beers over 8% abv. I rarely have two beers and almost never more than that. I drink usually 2x the water as I drink beer. t usually takes me about an hour to drink a pint. I wait an hour after drinking to drive. And I'm still nervous. How long do I have to wait until I'm safe?

I expect the answer will be "Your safety depends on a lot of factors" and "you're not safe to drive until you KNOW you are safe to drive" and also "Even being completely sober doesn't always mean you're safe to drive because there are other contributing factors."

But one of the things that's messing me up is - it's really hard to tell how I feel. I can feel completely fine, drive home, and then feel iffy again. But maybe that's just placebo? Or maybe I'm just extra tired and stressed. Or maybe dehydrated.

I would like to hear what rules of thumb other people have for making the decision, so that I can try to make better, safer decisions myself in the future.

posted by rebent to Grab Bag (23 answers total)

As you noted, there are many variables. Drink affects me in different ways (ask me about hangovers in my 40s) and I will never drive after drinking.

My rule of thumb is "just don't".
posted by Prof Iterole at 8:27 PM on April 21, 2017 [9 favorites]

the shorthand my physician father gave me was: if you can run down a flight of stairs with confidence, you're ok to drive.
posted by fingersandtoes at 8:33 PM on April 21, 2017 [9 favorites]

If it is that difficult for you to determine your level of safety, then please just do not drink if you will be driving. Please.
posted by blurker at 8:45 PM on April 21, 2017 [18 favorites]

You can always call a cab or an uber or have a friend drive you. I took part in a test once for the police to deal with intoxicated people and I ended up testing at 0.10 - almost legal to drive - but I wouldn't have driven a car for a million dollars in that state. Don't take a chance.
posted by kerf at 9:15 PM on April 21, 2017

Some info here about the Australian standard drink, which (despite the generally preachy YOUR HEALTHS tone) is a reasonable way of calculating. If your tolerance is (subjectively) low, less is always going to be better, as is finding alternative transport, but that is not always possible.

My general rule of thumb is 1 beer per hour and no more than 2 if I am due to drive. A pint counts as 2 drinks. With wine, it's 1 glass, 2 if with a meal. No spirits, because it's a) too hard to estimate, and b) not wise.
posted by prismatic7 at 9:17 PM on April 21, 2017 [5 favorites]

General rule of thumb: if you're actually fine to drive, drive. If you're probably almost certainly fine to drive, don't.
posted by so fucking future at 9:34 PM on April 21, 2017 [2 favorites]

Living in a country where any driving after drinking is illegal makes this problem super easy: walk, taxi or public transport. Done, and safe.
The problem is you don't know if you're impaired or not (especially if you're impaired!) And even if the legal limit did say you're ok to drive, but then you felt wonky while driving: that's not good for your safety either.
posted by sacchan at 9:47 PM on April 21, 2017 [2 favorites]

the shorthand my physician father gave me was: if you can run down a flight of stairs with confidence, you're ok to drive.

This is actually terrible, even irresponsible, advice as people routinely over-estimate driving ability and underestimate the effects of alcohol on reaction time, attention, perception, and more.

There is some excellent, advice based on research at the link above.
posted by smoke at 10:28 PM on April 21, 2017 [17 favorites]

No offense to anyone who already commented, but this is terrible advice. Does "Just don't drive after drinking" extend to the next... hour? day? week? And anything that relies on your own perception of how you feel – "if you're actually fine to drive, drive" – is deeply flawed.

You have two concerns:

1) Can you drive safely?
2) Can you drive legally?

If you trust the government's assessment that you can drive safely at .08 BAC, then you can lump those two concerns together.

You need to find out how your body's BAC is influenced by alcohol. Get a reasonably accurate BAC meter. Drink a very precise amount of alcohol over a precise amount of time. Note whether your stomach is empty or full. Test your BAC.

One factor that I think gets overlooked all the time is the definition of "a drink". You need to calculate the actual alcohol content of the drink. A 12oz bottle of Bud Light is a very different drink than an Old Fashioned made with a heavy 4oz pour.

If you need predictability, steer towards known beers in known quantities. Mixed drinks will be highly variable.
posted by reeddavid at 12:12 AM on April 22, 2017 [2 favorites]

If I can accurately sing "it's the end of the world as we know it," I'm good to drive. If I miss a single word, I hang out and drink water until I can do it right. It might seem silly, but it's worked for over twenty years.
posted by Ruki at 1:47 AM on April 22, 2017 [2 favorites]

This is an odd set of responses. You say youre a lightweight our that a half a beer impacts you. Great. Thats your limit. I know this is a thing etc but really, it's sooooooooo fucking easy, when you drive, never drink. Really. Not hard.
posted by chasles at 4:46 AM on April 22, 2017 [9 favorites]

Get a damn cab if you plan on drinking. Nobody can tell you with any certainty how your body metabolizes alcohol.

And frankly, if you're pickled after half a drink, just really please don't operate a vehicle at all on the same day you're drinking.
posted by Klaxon Aoooogah at 5:57 AM on April 22, 2017 [5 favorites]

My limit when I drive is one beer under 5% ABV. (That's not per hour, that's total.) I don't drive when I go out specifically to drink because I live in a city where cabs, Uber/Lyft, and public transit are plentiful, but sometimes I'll drive to a concert and just have one beer.

The cabs/rideshare/transit options don't exist in all cities or in suburban areas so I don't think this is an evil question to ask. I much prefer someone asking it to not, but I agree that if you feel even the slightest bit impaired you shouldn't drive. A single Miller Lite does not feel any different - to me - than drinking the equivalent amount of Coke, but I don't push it to 2 or more because the challenge is your perception of your own abilities changes along with your impairment.

I also keep my phone in my purse the entire time I'm in my car and never look at it or even talk hands-free, since it's been shown that having a conversation on the phone impairs you as much as a beer or two.
posted by misskaz at 6:00 AM on April 22, 2017 [4 favorites]

The answer is "tomorrow." You're OK to drive if you've slept 8 hours and aren't drunk anymore. Doesn't matter if it was half a beer or what. Get a cab. You might feel physically OK to drive after waiting an hour or drinking water, and there might be no incidents, but that doesn't mean you're not subtly impaired, and you're almost certainly not legal to drive in many states.

You could solve this problem by drinking at home, callng a cab, or being the designated driver. Good for you for thinking about it seriously!
posted by blnkfrnk at 6:27 AM on April 22, 2017 [3 favorites]

I am also like this. Not only do I get intoxicated quickly, but it takes me much longer than most people to sober up. After 1-2 drinks, it is typically 3-4 hours or more before I feel sober enough to consider driving.

This is obviously much longer than anyone wants to stay at a bar/restaurant. Therefore, I have decided that I simply have to choose between drinking and driving. It mildly stinks to go to happy hour with my coworkers and drink Diet Coke, but it's really OK; I still get to socialize. If I do want to drink, I take a rideshare service, or bum a ride from a friend who is safe to drive.

Also, for my job, I make computer models of how the human body processes drugs and chemicals. I specialize in simulating the variability from person to person. There are a lot of factors that could make someone's body behave very differently from the "average person." Standard assumptions like "it takes about an hour to process one drink, on average" may not apply. You and I both have evidence that our bodies just take a lot longer to process alcohol. We're out on the tails, far away from average. It's hard to predict exactly what our bodies will do without detailed, specific knowledge that would take a lot of expensive tests to find out.
posted by snowmentality at 7:10 AM on April 22, 2017 [9 favorites]

If by "lightweight" you mean "slow metabolizer," please note that you get the double-whammy of getting drunk from very little, and sobering up very slowly. So don't go by charts or methods for quicker metabolizers.
posted by kapers at 7:41 AM on April 22, 2017 [1 favorite]

The U.S. Federal Aviation Regulations (§ 91.17) prohibit operation of an aircraft within 8 hours of consuming alcohol. Airlines commonly have a stricter 12-hour requirement.

There are additional rules, including a BAC limit of 0.04.
posted by actionstations at 11:42 AM on April 22, 2017 [1 favorite]

I have sleep problems and I don't drive if I'm drinking, like, ever. I basically don't drive, it just gets rid of a lot of the type of anxiety it seems like you are having . I don't usually feel even tipsy after two beers but still..

So yeah, half a beer can mess you up? Don't drive after you drink.

I would also personally see a doctor because sounds like something is wrong, unless you're feeling weird after literally chugging half of an exactly 8% beer when you haven't slept well or eaten all day. That makes sense, but otherwise sounds like you probably have some other health issue where maybe driving for you isn't so good normally and a tiny bit of alcohol is just exacerbating the situation.
posted by love2potato at 4:56 PM on April 22, 2017 [1 favorite]

I bought a pocket breathalyzer. There are a bunch on Amazon. They might not be dead on accurate but it's better than guessing.
posted by poissonrouge at 6:07 PM on April 22, 2017 [1 favorite]

I was going to suggest a breathalyzer as well to see what your blood alcohol is in the situation you describe as well. Not to carry with you, just to help understand how you're metabolizing. Also because it's kind of fun.

For most light drinkers the US limit (0.08) is actually perceived as "Oh, I'm pretty drunk" or even beyond that. Not universally, but for a lot of us. A friend who worked for a crime lab told me this; it's certainly true for me. So you might feel tipsy at way lower levels (that one beer), and be at undetectable levels an hour later.

You definitely should not drive if you feel impaired, even if the breathalyzer says 0.02 or something. But it's implied you feel fine in the situation you're describing well before you're driving. If I did a breathalyzer and found I'm zero or almost zero under those circumstances, I would be willing to drive.
posted by mark k at 11:37 PM on April 22, 2017

It's possible the legal limit is well beyond what you'd consider remotely safe, it used to be very high in NZ and got brought down recently. A beer an hour is normally cited as the rate at which your liver metabolises booze, so is pretty universally safe, as long as you're not tiny or very hungry.
posted by Sebmojo at 1:48 AM on April 23, 2017

The drink server training I took awhile back said that, adjusting for size and factors such as metabolism, contents of stomach, hydration, etc., the rule of thumb is about one serving of alcohol per hour can be processed safely. I would say if you're planning on having a beer and know you will have to drive later, make sure you've eaten recently, continue drinking that water, and wait about an hour after finishing your drink before leaving to make sure you've had time to process it. And obviously, if after an hour you're still feeling unsteady or worried about it, consider taking an Uber or something instead. Stay safe! (Or drink at home! :)
posted by helloimjennsco at 7:44 AM on April 24, 2017

> I would like to hear what rules of thumb other people have for making the decision

I drove drunk once, just a few blocks before I realized what I was doing, abandoned my car, and walked the rest of the way home. I felt like such a jackass the next day (and also now, decades later). Now I don't drive after having even a single drink.

This can be annoying -- I like drinking -- but it's better than leaving the judgement to fellow lightweight, post-drink me.
posted by The corpse in the library at 12:28 PM on April 24, 2017