2 Answers

  To function properly, your blood requires healthy acid versus alkaline, or pH, levels. Systems in your body carefully maintain normal blood pH levels, which fall between 7.35 and 7.45, regardless of your diet. While water with lemon juice may alter the pH of your urine, it won't likely influence the overall acidity of your body. Learning more about the tangy beverage and your body's pH system may inspire you to make wise dietary decisions.

  On the pH scale, a score of 7 is considered neutral. Anything measuring 6.9 or below is considered an acid, and anything rating 7.1 and above is considered an alkali. While water has a pH of 7, lemons are acidic, measuring at 2 to 3. The popular belief that lemons become alkaline during digestion isn't upheld by science. Under no circumstances can an acidic food alkalize your blood, said Kat Day, a chemist and science blogger in Oxfordshire, England. Because foods are not known to alter the pH of your blood or body, lemons won't acidify you either. Drinking lemon juice with water may increase the acid level of your urine, however, which is a sign that your kidneys are doing their job -- ridding you of excess acid.

http://www.livestrong.com/article/498141-can-adding-lemon-juice-water-make-water-alkaline/

Lemon juice is acid, it contains citric acid.