Well man, if it was me I would go to the ER of a large public hospital where they can not refuse individuals without insurance. A very simple urine dipstick test will be done to see if indeed there is blood in the urine. You may very well be correct that it was due to dehydration, but I am guessing that you are probably a fairly young and healthy individual. Therefore, the chances of you getting severly dehydrated like that without running a marathon are slim. Also, dehydration causes the urine to turn dark yellow to orange. Certain senna based laxatives and rhubarb can also darken urine. Another possibility is a liver or gallbladder problem which would cause dark urine because of excess bilirubin. With this, you would likely have other signs such as jaundice (yellow coloration of the skin) and icterus (yellow eyeballs). You would also have very light clay colored stools. If the urine was green or blue, then I would tend to think that you ingested some food or medication with artificial coloring in it. That being said, in my experience, dark urine = blood until proven otherwise. Anything that damages the kidneys can cause blood in the urine. Bright red blood would be expected with trauma such as being punched in the kidneys. Darker blood is more worrisome. Another real possibility is that you could have had a renal cyst (which lots of people have) that ruptured. That is not anything to worry about. The things that I would consider most likely are cyst, infection, stone, and less likely some form of growth. As I said before, it will probably be nothing serious, but if it is and you wait then you may miss any opportunity for treatment and that is a risk that is just not worth taking. In the long run, it will be a few hours out of your life waiting in an ER, a urine sample, and possibly another radiologic test such as an IVP or CT scan. There are some bad things out there and worst case scenario, waiting as little as a month could cost you your life. I would advise you to see a doctor within the next couple of days. I have seen a lot of apparently young healthy people die because of similar things and I would not advise waiting. If you go and it turns out completely normal, then you can come on here and call me a big SOB, I wont mind.