Anytime you test yourself, always use the first urination of the day when THCA concentrations would be at their highest. Taking home tests in the latter parts of the day skews the results due to the consumption of fluids that happen during the normal course of the day. Once the fluids consumed had all been urinated out, the bladder is replenished with fresh THCA-laden urine by the kidneys, and thus the donor would resume testing positive for THC. This is the reason why drinking a bunch of water days or weeks before the U/A is of no help. For more info, do an Advanced Search, using the terms "drinking water useless" and/or "unaffected copius fluid consumption".

By using the first urination, youre testing yourself under the "worst-case scenario". If you test negative under that "worst-case scenario" (regardless of line intensity) then youre good to go.