If you find yourself making more trips to the restroom just before or during your menstrual cycle, you are experiencing a phenomenon commonly reported by many people. This increase in urinary frequency or urgency, known medically as polyuria, is a common cyclical symptom. This temporary shift is a direct result of the complex hormonal and physical changes occurring within your body during this phase.
Hormonal Shifts and Fluid Release
The primary reason for increased urination is the dramatic fluctuation of reproductive hormones that regulate fluid balance. During the luteal phase (the second half of the cycle), the hormone progesterone encourages the body to retain sodium and water in preparation for a potential pregnancy. This retention causes common premenstrual symptoms like bloating and temporary water retention, which is why some people experience slight weight gain.
When a fertilized egg does not implant, the levels of both progesterone and estrogen drop sharply just before menstruation begins. This sudden decline signals the kidneys to stop retaining fluid and start shedding the excess water and sodium accumulated over the previous two weeks. This process of increased urine production and excretion is called diuresis, which is the body’s natural way of eliminating retained fluid.
This natural diuretic effect means the kidneys work overtime to process and remove surplus fluid from your system, leading directly to more frequent bathroom visits. The volume of urine produced is often significantly higher than normal, intensifying the urge to urinate. This fluid shift is a temporary and necessary part of the body resetting itself for a new cycle.
Physical Pressure from Uterine Changes
Beyond hormonal effects, physical changes in the uterus also contribute to the frequent urge to urinate. The uterus and the bladder are anatomical neighbors within the confined space of the pelvis, with the uterus sitting immediately behind and slightly above the bladder.
During menstruation, the uterus becomes congested with blood and the endometrial lining, preparing to shed. The muscular walls also contract to expel this tissue, resulting in menstrual cramps. This combination of swelling, congestion, and contraction causes the uterus to physically expand and press against the adjacent bladder.
This mechanical pressure reduces the functional capacity of the bladder. Consequently, the bladder signals the brain that it is full much sooner than usual, even if it contains only a small amount of urine. Furthermore, prostaglandins, the hormone-like substances that trigger uterine contractions, may also irritate the bladder muscle itself. This increases the bladder’s sensitivity, making the urge to urinate more frequent and urgent.
When Increased Frequency Signals a Separate Issue
While increased urination is often a normal part of the menstrual cycle, it is important to recognize when this symptom might signal a separate health concern. If the increased frequency is accompanied by other distinct symptoms, consultation with a healthcare provider is warranted. A common separate issue is a urinary tract infection (UTI), which causes frequent urination and is sometimes mistaken for a typical period symptom.
A UTI is usually characterized by dysuria (a burning or painful sensation during urination), cloudy or foul-smelling urine, or blood in the urine. These symptoms are not typical of hormonally-driven polyuria and require medical attention. Other underlying conditions that cause excessive urination include uncontrolled diabetes mellitus, which leads to high glucose levels drawing excess water into the urine, or other kidney-related issues.
If the urinary frequency is extremely sudden in onset, persists long after your period has ended, or is accompanied by fever or back pain, a medical evaluation is necessary. Tracking your specific symptoms and their timing relative to your cycle can help determine if the cause is a normal fluctuation or a condition requiring intervention.