I just got my pH paper an ran many tests. My urine pH yesterday varied between 5.5 and 6.8 while the saliva pH varied between 5.8 and 7.0 during the day. I saw the pH drop after eating a piece of cherry pie and then go back up later in the day. I checked 10 times yesterday with the test strips.
This morning I tried 1/2 teaspoon of sodium bicarbonate and the pH went up from 5.8 to over 7 where the strips don't differentiate. I ordered some different strips to show more above pH 7.
I don't know what the numbers signify either. The urine numbers probably just show the acids removed from the body. The saliva should be more useful if done right. The problem of eating and drinking would affect the numbers and getting a good color from the blob of saliva was difficult.
My urine test sent to a lab about a year ago showed a pH of 6.5 after fasting for the testing with a normal range of 5.0 to 7.5. There must be a lot of variation with an average being more useful so one test wouldn't show much. The blood test then checked many things except showed no pH results. That was probably in the normal range then.
Both my urine and saliva react to adding sodium bicarbonate except the blood must stay about the same unless there was a serious problem as explained by pamojja.
I am probably going to continue with the added sodium bicarbonate. A study in India found that to be good for the kidneys and CKD after a 6 and 9 months of supplementation:
https://pubmed.ncbi.nlm.nih.gov/32269432/