Bloating peaks during the luteal phase, the stretch of roughly two weeks between ovulation and the start of your period. Most people notice it intensifying in the final five to seven days before menstruation, when both progesterone and estrogen are shifting dramatically. The sensation typically eases within a few days of your period starting.
Why the Luteal Phase Causes the Most Bloating
After ovulation (around day 15 of a 28-day cycle), your body ramps up production of progesterone and releases a secondary surge of estrogen. Both hormones have receptors in tissue far beyond the reproductive system, including the kidneys, the cardiovascular system, and the hypothalamus. Estrogen increases sodium reabsorption in the kidneys, which pulls extra water into your bloodstream and expands plasma volume. Progesterone partially counteracts this by decreasing plasma volume through its own effects on capillary fluid dynamics, but the net result during the late luteal phase is mild fluid retention that you feel as puffiness in your abdomen, hands, and breasts.
Research on fluid balance across the cycle shows that water retention begins roughly five days before ovulation, gradually climbs, and hits its highest point around menstruation. It drops to its lowest level right after your period ends. So while the bloated feeling builds through the luteal phase, the actual fluid peak lands in the final days before and the first day or two of bleeding.
Peak estrogen and progesterone levels coincide about eight or nine days after ovulation, roughly the midpoint of the luteal phase. From there, both hormones fall sharply if no pregnancy occurs. That hormonal free-fall in the last few days before your period is when PMS symptoms, including bloating, tend to be worst.
Progesterone Slows Your Digestion, Too
Fluid retention is only half the story. Progesterone directly acts on smooth muscle cells in your gut, reducing their ability to contract. This slows the pace at which food moves through your intestines. Slower transit means more time for bacteria to ferment what you’ve eaten, producing gas that stretches the intestinal walls and adds to the bloated feeling. Studies on colon smooth muscle show that progesterone inhibits resting tension and contractile strength in both the stomach and the large intestine by binding to receptors on the muscle cell surface.
This is also why constipation is more common in the days leading up to your period. The combination of extra water being held in tissue (rather than in the bowel) and sluggish intestinal movement creates a one-two punch that makes your abdomen feel tight and distended.
Bloating Around Ovulation
Some people also notice a shorter burst of bloating around mid-cycle, when the egg is released. This happens for a different reason. The follicle containing the mature egg grows rapidly, stretches the ovary’s surface, and then ruptures. Fluid or a small amount of blood from the follicle can irritate surrounding tissue, causing temporary abdominal fullness and sometimes a sharp, one-sided pain called mittelschmerz. This ovulation bloating is usually mild and resolves within a few minutes to a couple of days, far shorter and less intense than the luteal phase version.
When Bloating Eases
For most people, the relief arrives within the first two to three days of menstruation. As hormone levels bottom out and then begin rising again in the new follicular phase, your kidneys release the extra sodium and water, gut motility picks back up, and the distension settles. If you track your cycle, you’ll likely notice that the days right after your period ends are when your abdomen feels flattest.
What Actually Helps Reduce It
Sodium intake has the strongest evidence behind it. A randomized controlled trial testing different sodium levels found that high sodium intake increased the risk of bloating by 27% compared to low sodium intake, regardless of what else participants were eating. Cutting back on processed foods, salty snacks, and restaurant meals in the week before your period can make a noticeable difference. This doesn’t mean eliminating salt entirely. It means being more deliberate about it during the days when your body is already primed to hold onto sodium.
Magnesium supplementation also has some support. A double-blind crossover study found that a daily combination of 200 mg of magnesium with 50 mg of vitamin B6 reduced anxiety-related premenstrual symptoms. Magnesium plays a role in muscle relaxation and fluid balance, which may help with both the water retention and the digestive slowdown. If you eat plenty of leafy greens, nuts, and seeds, you may already get enough, but many people fall short.
One counterintuitive finding: high-fiber diets can actually increase bloating in the short term, even though they’re healthy overall. The same trial that showed sodium’s effect found that participants on a high-fiber diet (about 32 grams per day) experienced more bloating than those on a lower-fiber diet. Reducing sodium on a high-fiber diet helped offset that effect. So if you’ve recently increased your fiber intake and feel more bloated premenstrually, dialing back your salt may be more productive than cutting the fiber.
When Bloating May Signal Something Else
Normal cycle-related bloating is uncomfortable but predictable. It follows a clear monthly pattern, builds gradually, and resolves with menstruation. If your bloating is severe enough to visibly distend your abdomen, comes with significant pain, or worsens dramatically around your period, it may point to endometriosis. A specific pattern called “endo belly” involves extreme abdominal distension that intensifies with menstruation due to endometrial tissue growing outside the uterus. People with endometriosis often have a lower stretch pain threshold in the intestinal wall, which means even normal amounts of gas can feel significantly more painful.
Bloating that doesn’t follow a predictable monthly rhythm, instead flaring in response to certain foods, stress, or without clear triggers, is more consistent with irritable bowel syndrome. The distinction matters because IBS bloating and endo belly look similar on the surface but have different underlying causes and different treatment paths. Endometriosis also commonly shows up alongside painful periods, pain during sex, and sometimes difficulty getting pregnant, though it can also present with vague digestive complaints that mimic other conditions.