Hi thanks for your question.
40 mg of lasix
should be able to cause lot of urination, unless you have an organic obstruction (obstruction in urinary tract) or renal failure
. Blood in urine could be due to urinary tract infection
or due to stone. Possibility of stone is more likely as you were unable to pass urine after lasix.I would suggest you to consult a physician who will be able to evaluate you for your symptoms.
You need, plain x ray abdomen, ultrasound
abdomen and urine examination.
Hope this answers your question.