From my own mountaineering experience, I cannot say with certainty that I urinate more at high altitude. But there are plenty of claims, some probably based on evidence, that this indeed happens.
There is a medical term altitude-induced diuresis which describes the fact that during the initial phases of altitude acclimatization people urinate more.
According to an article, this happens because of the following. Lower level of oxygen is sensed by kidneys which release erythropoetin hormone that is behind increased production of red blood cells. This happens as a natural reaction of our body. It increases the oxygen-carrying capacity of the blood.
With increased red cells, our body tends to dump extra fluid, and this results in excess urine. The process eventually reduces as we become acclimatized. But there is more to this as described below.
Increased urination and perspiration belong to sensible fluid losses. This is a natural adaptation in which our blood becomes thicker and hemoglobin becomes more concentrated. This should result in more oxygen to your muscles and organs.
But there are also insensible losses due to vaporization through the lungs and skin. Due to lower relative humidity with altitude and increased ventilatory rates, these insensible losses may be huge.
Clearly all these sensible and insensible losses must be compensated with an increased water consumption.
It seems there is more to this. Apparently, increased urination is also a way of avoiding respiratory alkalosis (which means elevated blood PH) by kidneys’ excretion of bicarbonate. Eventually, our body adjusts and this alkalosis is regulated as we become acclimatized.
Finally, because of low temperatures at higher elevations, our body reacts by eliminating a part of out body fluid by urination, and this all to reduce energy for heating it. I guess this effect should be taking place in cold weather in general.
Here a few more thoughts on these all issues, have a look:
What is normal urine output?
From what I can find, it appears that the normal urine output is in the range 0.8 to 2 liters per day. This is assuming a normal fluid intake of about 2 liters per day.
But I wonder what one can do with this. If you are high in the mountains, you will measure your urine output. Are you gong to collect it in a bottle?
On the other hand, what is ‘normal’? Do you know your personal urine output? I certainly do not know it, have not measured it ever. Why should I?
So in practice, it is hard to know if we pee more than usual or not. Now you realize why I started with the statement above, saying that I am not sure about an increased urination.
But there were experiments performed to check the effect of drinking tea at altitude. So they were able to measure and to get to some conclusions.
What is normal urination frequency?
Here, it seems the number is 6 – 7 in a 24 hour period. But I can tell you immediately, this does not apply to me. I think the term ‘normal’ is very difficult to apply to anybody. We are all different.
It seems the only way is to pay attention and record the number when you are at home. Then compare it with what you experience in the mountains. This will be the only reliable information for you.
In any case, after reading all the stuff related to this issue, it is possible that my hydration may not be adequate. But to be completely sure, I would have to measure i) the urine volume and ii) urination frequency. After that I would have to compare it with these parameters from home conditions.
Some people even feel more gassy at high elevations. Let me know what you think about these issues, and do you urinate more at high altitude, there is a comment box below.
You might want to check also my separate text which is about yet another altitude-related question ‘do people poop more at higher elevations‘. Also, did you hear about reverse altitude sickness? Thank you for reading and have a nice day.