Ammonia breath / smell

I’ve noticed that when showering after hard workouts, I sometimes smell ammonia or a distinct chemical aroma. I thought it was that exercise somehow altered my sense of smell and I was smelling the chemicals in my shampoo, until I read this TrainerRoad blog post:

In it, Coach Chad writes, “Once your muscle stores are deficient of glycogen, you can expect to hit a wall in your workout, unless your intensity stays fairly low. How soon until that fatigued feeling consumes you will depend on the intensity of your workout. … One way to tell you’ve crossed that line is the smell of ammonia on your breath.” So I assume that it wasn’t that exercise was changing my sense of smell, it was changing my breath, which is what I was smelling.

What is confusing me, however, is that I haven’t felt unusually tired during the times this has happened to me. Obviously, I’m the normal amount of tired after a hard workout, but I didn’t feel like I was hitting a wall or bonking or anything like that. So – assuming that my performance isn’t suffering – it this state dangerous? I never notice this “in the moment”, during my workout, I only notice it afterwards (like I said, usually in the shower). I’m trying to figure out whether this is something I need to worry about and have some other way of detecting while its happening, or whether I can safely ignore it unless my performance suffers…

Note that I haven’t previously been consciously trying to engage in fasted workouts, but I do intend to do so going forward (partly to lose weight), which is how I came across the above blog post in the first place.

Many thanks in advance for any advice / insight you can provide,

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Isn’t ammonia breath associated with ketosis?


I have not observed ammonia smell on my breath, however, lately I can just about set a timer for when my towel starts to smell strongly of ammonia. I just finished my version of SSBII HV and about 90-100 minutes into the 2hr SS rides my towel would take on the ammonia odor. Up until that point it would just smell like my normal sweat.

Like you I do not feel unusually tired, and I’m able to complete the final 30 minutes without issue. This year I’ve been focusing on pushing my limit for calorie/carb consumption during these 2hr SS rides. They are far from fasted. Last weekend I consumed 700-850 calories on each of my 2hr SS rides. I did this with sports drinks, dates, clif bloks and gu waffles. This is after having breakfasts consisting of fairly easily digested carbs: cereal, milk, english muffins, jam, oatmeal, maple syrup and honey.

I’ve been perplexed by this, but have not made any detrimental observations to my training. I’m mostly pleased with how my body responded to HV SSB. I make sure to get recovery drink and food in me asap after these rides.

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The smell of ammonia during hard work is typically associated with the breakdown of muscle during workouts that are extremely difficult and insufficiently fuelled.

After a little bit of research, this could also have to do with breaking down dietary protein for fuel, perhaps if you workout right after breakfast where you eat eggs with no toast. Or it could be a result of not drinking enough.

Definitely first look at hydration and diet, if you’re not feeling aches afterwards it is unlikely to be muscular breakdown.

Hmmmm…I just found this:

But I still can’t figure out whether this is something to be concerned about or not. Like I said above, I am trying to include some fasted workouts in my exercise routine to lose weight. Since they are fasted, it seems unlikely that this is resulting from the breakdown of dietary protein. And I’m not bonking during my workout, nor do I ache afterwards, so I hope I’m not breaking down my body’s muscle fiber.

If I am breaking down muscle fiber, then I will have to eat more carbs before / during my workouts, but that is certainly something I would like to avoid, if possible.

I will post to say that I’ve noticed the same thing. I am well fueled and have been adding muscle during SSB 1/2 so I am doubtful that I’m burning muscle but not completely closed to the idea.

Will be interested to hear if someone has additional info.

This is my experience also. It actually seems to be happening more since I started fueling my workouts more by both adding carbs to my breakfast and then eating carbs during the workouts. I do eat a bunch of protein in the morning (~3h before workouts), too, though.

It’s purely down to a lack of sufficient carbohydrates


Yes, which is due to a lack of carbohydrate or to be more precise burning fat. Here is a link which may help you

If I’m burning fat, that’s exactly where I want to be. If I’m burning protein (specifically muscle as opposed to dietary protein), that’s bad.

In the TrainerRoad blog post I linked to above, Coach Chad seems to indicate that once you have ammonia on your breath, you’ve crossed a bad line, and therefore he recommends “Something like a sports drink or even a gel washed down with plenty of water” to get back on the right side of the line.

Or am I misreading his advice, and that is only necessary if you “hit a wall in your workout”, but otherwise it’s totally fine (and maybe even a positive sign of fat burning)?


If you’re not fat adapted and don’t eat enough carbs you’r body will consume protein

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Ketosis makes your breath smell like acetone, which is quite different from ammonia. This is not a ketosis effect.

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The first thing I’d recommend here is double checking your hydration. Mix up 2 bottles of something like a Skratch labs hydration mix, start drinking it before you’re on the bike and get through as much as is comfortable. See if that helps.

Wouldn’t this occur on almost every workout then? I never consume the amount of calories that I burn for any ride. If it’s a 700 calorie Pettit ride I consume water, if it’s a 1,500cal SS ride I can take in about 850cal max. I do get that I’m starting with some fuel in the tank.

My off the bike diet is very different from on the bike food. I’d say it probably has a higher % fat than an average persons. I still eat pasta, rice, beans and potatoes though.

Now that I completed SSB I’m scheduled to do an Inbody composition scan tomorrow. The last one I did was on day 2 of SSB. Perhaps that will provide insight on changes in muscle composition. Next week I’m doing my first DXA scan so I won’t have any previous data for comparison. Will be able to compare it to the Inbody scan.

In terms of hydration a 2hr SS ride is automatically 4 bottles for me, 2 of which have tailwind or some other hydration mix.

I just want to make sure I’m not doing something severely detrimental to all the training I put in.

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This won’t help you lose weight. Eating in a caloric deficit will. As long as you’re getting sufficient protein and rest, you’re going to minimise (and possibly negate) any breakdown of muscle while the fat comes off, it will depend on how severe you cut calories.

@purgatos – To be honest with you, I may be confusing the smells of acetone and ammonia. To me it is a distinctly chemical smell that is fairly sharp, but I’m not sure whether it is acetone or ammonia. I’ll try to pay attention the next time I smell it. I may have just assumed it was ammonia after reading the blog post. It also isn’t clear to me that it is necessarily my breath. It’s also possible that I’m smelling my sweat – I’ve never really noticed where the smell was coming from, because I always assumed it was just my sense of smell playing tricks on me, not an actual chemical change in my body.

For what it’s worth, I’m confident my hydration is pretty good. I drink a lot of water, occasionally with either Nuun tablets or a pack of the WHO-recommended hydration powder added. And my workouts seem comfortable (or rather, as uncomfortable as you would normally expect vigorous exercise to be - i.e., not subjectively bad in any way) and I’m not having any trouble getting through them.

@TommyTomkins I am in a caloric deficit. I’m using the fasted rides to get in some light work (and burn additional calories) before my more intense fueled rides later in the day.

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Typically ketosis will not happen by accident. I would probably discount it unless you are intentionally following a very low carb diet, in that case I would say it’s definitely possible.

With the information that you are in a caloric deficit and doing fasted rides in the morning, I think burning protein is the more likely situation. Something may have to give here, either reducing your caloric deficit so that you are better fuelled for your morning rides(better for getting faster on the bike) or keep your deficit the same and reduce the time you are spending on the bike in the morning(better for weight loss).

If there’s a possibility that it’s just breakdown of dietary protein and it really only happens “sometimes,” it’s probably not the worst thing in the world, either, right? I am by no means an expert not even to speak of having any medical credentials, though.

Sure it’s you? I’m 90% kidding, but since you said specifically that it’s “when showering” and that you don’t feel like you’re being eaten alive, I couldn’t help wondering whether there might be baby diapers or a cat box in the same space. :smiley_cat:

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