Interstitial cystitis:

A condition characterized by pain in the bladder and pelvis, often accompanied by a frequent urge to urinate.
Diuretics:

Medications used for high blood pressure or kidney problems can increase urine production, thus increasing the frequency of urination.
Neurological diseases:

A stroke or other neurological condition can damage the nerves that supply the bladder, causing a frequent and urgent need to urinate.
Hypercalcemia:

High blood calcium levels, caused by thyroid or parathyroid problems, diseases such as tuberculosis, or some types of cancer, can lead to frequent urination.
Diabetes insipidus:

This condition arises from a defect in the pituitary gland, which affects fluid balance and causes excessive urination.
Overactive bladder:

Involuntary bladder contractions lead to frequent and urgent urination even when the bladder is not full.
Less common causes:

Bladder dysfunction, pelvic radiation therapy, excessive caffeine consumption, kidney disease, cirrhosis, chronic diarrhea, and Cushing’s syndrome can also contribute.
Causes of frequent urination in men:
Prostate enlargement, a common problem with age, can lead to increased urgency due to pressure on the urethra. Other reasons mentioned may also apply.

Causes of frequent urination in women:
Possible causes include pregnancy, bladder and ovarian cancer, vaginitis, pelvic organ prolapse, and psychogenic polydipsia.

Normal urination frequency:
On average, a healthy person should urinate 6 to 8 times a day. Factors such as water, caffeine, or taking a diuretic can affect this. Urinating every hour is abnormal and may be caused by changes in diet, medications, or underlying health problems.

Diabetes and urination:
People with diabetes may produce more than 3 liters of urine per day, and urinate about 10 times or more due to the elimination of excess glucose.