What causes false negative hpt? is it common?

Does happen: Some things that can cause a false negative HPT: Taking the test too early; Checking the results too soon (you have to read instructions and set a timer); Drinking a lot of water can dilute your urine and give you a false negative (first am urine is most concentrated). A pregnancy that isn't doing well such as an ectopic pregnancy sometimes doesn't make enough hormone to turn a test positive.