We've all heard stories about how people saved their lives by drinking their urine. Is drinking urine safe when there are no other water sources available? Can I filter it with a water purifier?
Assuming you don't have a genitourinary tract infection, fresh urine should be sterile, the problem is that it is a waste product which, apart from making it not taste very nice, means that consuming it will increase the concentration of waste in your body which will require an increased volume of water to absorb and subsequently excrete, resulting in you being more dehydrated. You could distil urine using a solar still to overcome this problem, such as this method, however, I wouldn't expect a filter (at least those designed for outdoor activities) to remove the salts and other waste compounds found in urine.
I've also heard of using urine to moisten your lips to lessen the symptoms of dehydration.
Copy and paste from the answer here: Is it a good idea to drink your own urine in a survival situation (Skeptics SE)?
Summary: You can do it, as a last resort, but it's dicey.
The US Army doesn't think it's a good idea and lists it on its "Do NOT drink" list, stating in its Field Manual that it "contains harmful body wastes" and that it is "about 2 percent salt." Several other resources seem to agree, all indicating that it will increase your rate of dehydration. (Warning: the popular science link is not fun to open.)
If it's your only source of water, it's likely that the US Army's recommendations of how to purify polluted water for consumption also applies to urine:
If polluted water is your only moisture source, dig a small trough outside the hole about 25 centimeters from the still’s lip (Figure 6-8). Dig the trough about 25 centimeters deep and 8 centimeters wide. Pour the polluted water in the trough. Be sure you do not spill any polluted water around the rim of the hole where the plastic sheet touches the soil. The trough holds the polluted water and the soil filters it as the still draws it. The water then condenses on the plastic and drains into the container. This process works extremely well when your only water source is salt water.
Other sources, which support my memory on the matter, indicate that it is at best a short term solution. For example, in a Slate article named The Yellow Liquid Diet, the author says that the waste might eventually "cause symptoms similar to those brought on by total kidney failure":
How long can you survive by drinking pee?
An extra day or two, at best. A healthy person's urine is about 95 percent water and sterile, so in the short term it's safe to drink and does replenish lost water. But the other 5 percent of urine comprises a diverse collection of waste products, including nitrogen, potassium, and calcium—and too much of these can cause problems. When you drink your own pee, all the stuff that your kidneys had attempted to excrete comes right back into your stomach, and much of it ends up back in your kidneys. After several days of this, your urine will become highly concentrated with dangerous waste products, and drinking it can cause symptoms similar to those brought on by total kidney failure. At that point, you're doomed either way—from dehydration on the one hand or renal meltdown on the other. (Even if one could filter out most of the unwanted products in urine, the cycle would not be sustainable for long. In addition to what he or she pees out, the average human excretes about half a quart of water a day through sweating and exhaling.)
However, drinking urine for survival has been attempted successfully before.
For example, in 2008, a Chinese man by the name of Shen Peiyun survived six days by lying still and drinking his own urine, which is solid evidence that it won't kill you at least some of the time. While it is not necessarily fatal, it doesn't mean it isn't harmful. For instance, in the case above, no expert has asserted that he would have died without drinking his own urine.
Urine is normally sterile (barring urinary tract infections) - so, from bacteriological stance, fresh urine isn't going to hurt.
The problem is - urine is a waste product, and so is full of stuff that your body wants to be rid of. Worse, as you get more dehydrated, your body produces more concentrated urine. That said - as a short term measure to keep hydrated, it can be drunk.
I remember my military survival training - we were instructed how to make a filter using a sock filled with dirt. It isn't the most efficient filter, and probably tastes pretty awful. If you have a ceramic filter, that might be better, but I'd imagine there's still be a flavour.
I have read of a case where people survived in a life raft not by drinking their own urine, but by rectally infusing urine through a tube.
This is apparently quite a safe way to get your body to extracting the water in a fluid without absorbing all/too many of the potentially dangerous waste products.
Turns out one of the survivors was a nurse and new how to place a rectal catheter - lucky them. :P
I can't find the actual link to these survivors story, but here is an article describing rectal fluid infusion as a means to rehydrate people: Emergency rectal infusion of fluid in rural or remote settings