Other reasons the urine test can be incorrectly negative is when it's not done properly by the patient ( who is not an expert, after all, and can make errors !); and if the urine is too dilute ( so that the concentration of the HCG in the urine is too low for it to be picked up by the urine test). This is why an
IVF clinic will never rely on a urine
pregnancy test and will insist that the patient do a blood test to check their
HCG level.