Hello,
Without examination confirmation of a diagnosis is tough but frequent urination (polyuria) can be due to diabetes mellitus. Other possibilities are diabetes insipidus, glomerulonephritis, pyelonephritis(inflammation of the kidneys),urinary tract infection, hypercalcemia, hypokalemia(low potassium),hyperthyroidism, hyperparathyroidism, diuretic drugs and benign hyperplasia of the prostate(in males).
In my opinion, investigations like kidney functions, blood sugar levels, ultrasound lower abdomen , intravenous pyelography ,prostate specific antigen blood test, thyroid function tests and cystoscopy may be needed to confirm a diagnosis. I sincerely advice you to consult a urologist or nephrologist for your husband and get him evaluated so that a confirmatory diagnosis can be made.
I hope it helps. Take care and regards.
he could possibly have an enlarged prostate. He should go to his doctor.