Interesting question, Michael. I think that the whole obsession some seem to have with acid/base balance is misplaced (see also here and here for previous discussions).

Urine pH between 4.5 and 8 is normal. Urine pH varies depending on your diet and even the time of day. Your urine will tend to be acidic early in the morning. Meat-eaters tend to have more acidic urine than vegans/vegetarians. In fact, vegans exploit this difference to argue the whole "alkaline=good, acidic=bad" concept.

Urine pH can be used in screening for some kidney, metabolic and respiratory diseases. There are also rare cases when one may want to manipulate urine pH. For example, some kidney stones form in acid pH, while some form in alkaline pH. Some poisonings, such as aspirin, can be treated by alkalinizing the urine.

However, if you are healthy, you do not need to check or worry about your urine pH. When I went to medical school, there was an aphorism on the wards--"The kidneys are smarter than we are." So let your kidneys do their job(s), and don't try to over-think your body's acid/base balance.

Reference

I agree with Ed's response about vegan claims about urine pH complicating its significance. I tried measuring urine pH during my short burst of interest in raw veganism. I was still eating chicken occasionally, but everything else in my diet was consistent with a eating gluten-free, soy-free raw vegan diet. In all honesty, I found the whole process highly confusing because of all the different vegan claims that mention alkaline/acid balance. I usually registered at something around 5 or 6, even if I went authentically raw vegan for weeks. I can see the change in urine pH not being instant, but I was pretty dismayed that I couldn't even hit alkalinity after weeks. One day I ate chicken and a few days later, I hit 7 and was super excited. But then I saw a raw vegan website claiming that if a meat-eater has an alkaline reading on urine pH then that just means that our poor bodies are pulling calcium from our bones to neutralize the acid-creating meat, which is even more dangerous. Also super confusing to me because it meant that even alkalinity readings couldn't be taken at face value and needed to be treated as acid readings. According to the vegan theory of it, it seemed like my would never genuinely reach alkalinity if I responded to my body's craving for real protein. At the end of the day, I've found that I feel 1000% better on paleo that I did experimenting with raw veganism, so that's more meaningful for me than urine pH.

But that might just have been my own weird experience with urine pH. Some Whole Foods sell the ph testing tape, so it's fairly easy experiment to do.

PH tests of urine only measure the acid base balance of your urine which can vary by quite a lot depending on what you ate just recently. If you did the same test in your stomach, you'd get a different measurement. If you did the same test on your blood, you'd get a whole 'nother measurement. The PH of various parts the body are different. THe body keeps blood PH in a very narrow range, unlike the variances allowed in the gut. There is no evidence that one kind of food makes a difference in blood PH. Blood PH is only threatened when your body is unhealthy and its many PH balancing mechanisms, like breath regulation, are not working properly. THere is not a molecule of evidence for the whole acid/base theory. However, I do think that a lot of the foods (but not all) that it recommends you don't eat tend to be on the healthy side so I would not be surprised if many people would feel better if they eliminated or cut back on those foods.