The week or so before a period is when many women notice they are warmer at night, hungrier in the afternoon, puffier around the middle, and a little less patient with the world. None of that is imagined, and none of it is a flaw. It is the signature of one hormone doing its job.
That hormone is progesterone, and the stretch of the cycle it governs is the luteal phase. This article explains what progesterone does and what the research says about the four things people ask about most: bloating, cravings, sleep and mood. It also draws the line between an ordinary luteal phase and premenstrual syndrome.
For the whole cycle laid out first, start with The Four Phases of the Menstrual Cycle.
What the Luteal Phase Is
The luteal phase begins when an ovary releases an egg and ends on the first day of the next period. It is named for the corpus luteum, Latin for "yellow body," which is what the emptied follicle becomes after ovulation: a small temporary gland whose purpose is to make progesterone, along with some estrogen.
The corpus luteum has a built-in lifespan. If a fertilized egg implants, a signal from the early pregnancy keeps it going. If not, it degrades after roughly two weeks, hormone levels fall, and the uterine lining it was maintaining comes away as a period. That fixed timer is why the luteal phase is the more predictable half of the cycle. In a 2019 analysis of more than 600,000 ovulatory cycles published in npj Digital Medicine, the mean luteal phase was 12.4 days with a standard deviation of 2.4 days, while the follicular phase before it averaged 16.9 days and varied far more. (The data came from a cycle-tracking app and the study was company funded, so read the precise figures as indicative.)
Progesterone: The Hormone Running the Show
Progesterone's first job is in the uterus. During the follicular phase, estrogen built up the lining. Progesterone now changes its character, making it secretory and nutrient-rich, ready to support an embryo. It also calms the uterine muscle so the lining is not disturbed.
But progesterone does not stay in the pelvis. It acts on the brain, the body's thermostat, fluid balance, the gut, and the pathways that regulate sleep and appetite. Estrogen is still present, with a second smaller rise mid-luteal, but progesterone is the dominant signal.
Then, in the last few days before the period, both hormones fall sharply together. That withdrawal, rather than the high levels themselves, is what many researchers think triggers premenstrual symptoms.
Why Your Temperature Rises
One of the most measurable effects of progesterone is on body temperature. A 2014 review in Comprehensive Physiology by Charkoudian and Stachenfeld summarizes the physiology: estrogens generally encourage heat loss and lower core temperature, while progesterone and related progestins push in the opposite direction, acting on the temperature set-point in the hypothalamus.
The size of the shift is small but reliable. Core body temperature runs about 0.3 to 0.4 °C (roughly 0.5 to 0.7 °F) higher in the luteal phase than in the follicular phase, according to a 2010 review by Shechter and Boivin in the International Journal of Endocrinology. The usual overnight dip in temperature is also blunted, so the difference is most noticeable at night and on waking.
This is the basis of basal body temperature charting. Because the rise appears only after ovulation, a sustained step up in your waking temperature confirms that ovulation has already happened; it cannot tell you it is about to. It is also why some women feel warmer in bed or wake slightly sweaty in the premenstrual week.
Bloating and Fluid Retention
Bloating is one of the most common luteal-phase complaints and one of the least understood. The usual explanation is that progesterone, or the drop in it, makes the body hold water. The best prospective data complicates that story.
A 2011 study in Obstetrics and Gynecology International followed 62 healthy women through 765 menstrual cycles over a year, with each woman rating her sense of fluid retention daily on a 0 to 4 scale and ovulation confirmed by temperature analysis. Self-rated fluid retention was lowest in the mid-follicular phase, rose gradually across the days around ovulation, and peaked not in the premenstrual days but on the first day of menstrual flow, with a mean score of 0.9. Measured estradiol and progesterone levels were not significantly associated with the fluid scores, though hormones were only sampled in two cycles per woman, which limits how firmly that null finding can be read.
So the puffiness is real and cyclical, but it tracks the premenstrual-to-menstrual transition rather than the whole luteal phase. And bloating is not the same as measurable water gain: progesterone also slows gut motility, which can mean more gas and fullness independent of fluid.
The American College of Obstetricians and Gynecologists lists bloating, weight gain and swelling of the hands or feet among the physical symptoms of PMS, and suggests reducing salt before a period as a simple first step. It also notes that magnesium supplements may help with water retention and breast tenderness, though the trials behind that are small.
Cravings and Appetite
If you are hungrier in the week before your period, you are reading your body correctly. This is one of the better-documented luteal-phase effects, though the exact size is still debated.
A 2023 narrative review by Rogan and Black in Nutrition Reviews found that higher energy intake in the luteal phase than in the follicular phase was the most consistent pattern across studies, with most reporting a difference of roughly 200 to 350 kcal per day, and intake lowest in the days leading up to and including ovulation. The authors were candid about the limits of the evidence: inconsistent methods for confirming cycle phase, few studies tracking more than one cycle, and very little data on highly active women.
A 2025 systematic review and meta-analysis in the same journal, by Tucker and colleagues, pooled 15 datasets covering 330 women and reached a similar conclusion: energy intake was higher in the luteal phase by an average of about 168 kcal per day, with a moderate pooled effect size. Heterogeneity was high, and only three studies verified cycle phase with more than one method, so the precise number is uncertain.
Why would appetite rise? A review by Davidsen, Vistisen and Astrup in the International Journal of Obesity (2007) noted that energy expenditure also rises in the luteal phase, so part of the extra intake is the body matching a slightly higher metabolic cost, including running a fraction of a degree warmer. The same review reported more frequent cravings in the luteal phase, especially for carbohydrate-rich and fat-rich foods.
The practical message is reassuring: an extra 150 to 350 kcal a day for a week or so is modest, partly offset by higher expenditure, and not a sign of lost discipline. ACOG's advice for this part of the cycle is to lean on complex carbohydrates, eat smaller meals more often to keep blood sugar steady, and go easy on sugar, salt, caffeine and alcohol.
Sleep in the Second Half of the Cycle
Many women say they sleep worse before a period. Laboratory studies broadly agree, with some nuance about what changes.
The clearest summary comes from the 2010 review by Shechter and Boivin and a 2018 review by Baker and Lee in Sleep Medicine Clinics. Across polysomnography studies in healthy women:
- REM sleep decreases in the luteal phase. This is the most consistent finding.
- Sleep spindle activity increases, most markedly in the late luteal phase. Spindles are brief bursts of brain activity in light sleep, and the rise is thought to reflect progesterone and its metabolites acting on the brain.
- The temperature rhythm flattens, which may matter because a falling core temperature is one of the signals that helps sleep begin.
- Sleep onset, total sleep time and sleep efficiency are mostly unchanged in objective recordings, even though subjective sleep quality is often worse in the late luteal and premenstrual days.
In other words, healthy women tend to feel that they sleep worse before a period more than the monitors show. That gap narrows for women with premenstrual symptoms: Baker and Lee report greater self-reported sleep disturbance in the premenstrual and menstrual phases, particularly in women with premenstrual symptoms or painful periods, and Shechter and Boivin note that in premenstrual dysphoric disorder, insomnia or excessive sleepiness is reported by as many as 70 percent of women.
Mood, Serotonin and the Premenstrual Days
Lower mood, irritability and tearfulness in the days before a period are extremely common. Why they happen is only partly understood.
The most important single experiment is a 1998 study by Schmidt and colleagues in the New England Journal of Medicine. Women with and without premenstrual syndrome were given a medicine that switched off ovarian hormone production. In the women with PMS, symptoms disappeared. The researchers then added back estrogen or progesterone under double-blind conditions: symptoms returned in the women with PMS, but the same hormones changed nothing in women without it. The authors' conclusion was that premenstrual symptoms reflect an abnormal response to normal hormonal changes, not abnormal hormone levels.
The leading candidate for that response is the brain's serotonin system. A 2008 review in The Lancet by Yonkers, O'Brien and Eriksson describes two families of approach known to work for severe premenstrual symptoms: those that stop the ovarian cycle, and those that act on serotonin signaling. Serotonin reuptake inhibitors work even when taken only during the luteal phase, a strong clue that serotonin sensitivity changes across the cycle. The same review estimates that about 5 to 8 percent of women have severe PMS by its definition; the stricter criteria for premenstrual dysphoric disorder give 2 to 5 percent.
Serotonin may also connect mood to the carbohydrate cravings described earlier. Eating carbohydrate raises the availability of the amino acid from which serotonin is made, and one long-standing hypothesis is that premenstrual carbohydrate craving is a form of self-correction. It is plausible, with partial support, rather than established.
For most women, premenstrual mood changes are mild, predictable and gone within a day or two of bleeding starting. When they are not, that is PMS or PMDD.
Living With Your Luteal Phase
None of the research above says the luteal phase is a problem to be solved. It says the luteal phase is a slightly different state: warmer, hungrier, lighter-sleeping and more sensitive. Living with it well is mostly a matter of expecting it.
- Track it. Knowing your period is due in four days reframes a bad afternoon. The Office on Women's Health and ACOG both recommend a daily symptom diary over two to three cycles.
- Eat to the hunger, within reason. The extra appetite is real and partly matched by extra expenditure. Regular meals with complex carbohydrates and protein beat skipping and then overshooting.
- Protect sleep. Keep the bedroom cool, since your thermostat is set higher this week, and keep bed and wake times steady, which ACOG recommends for premenstrual moodiness and fatigue.
- Keep moving. ACOG notes that regular aerobic exercise, around 30 minutes most days and throughout the month, lessens PMS symptoms for many women.
- Lean on warmth and ritual. Many food traditions, including the Chinese one, regard the week before a period as a time for warm, cooked, gently spiced food and warm drinks. In Chinese medicine the premenstrual days are also when warming, moving recipes such as Wen Jing Tang are traditionally taken, on the theory that a well-warmed uterus bleeds on time and without cramping. The clinical evidence for most of these foods is thin, but the habit of sitting down with something warm is harmless and, for many women, steadying. We cover the tradition, and what the trials do and do not show, in Foods and Teas Traditionally Taken Around Your Period.
The Fourth Trimester makes teas from dried culinary and herbal ingredients, drawn from recipes traditionally prepared in China around the menstrual cycle. That is the tradition behind our Premenstrual Tea.
Explore the Menstrual Cycle rangeWhere PMS Sits
Everything described so far is the normal luteal phase. Premenstrual syndrome is when the same changes become severe and regular enough to interfere with life.
ACOG's patient guidance sets out the pattern a clinician looks for: symptoms present in the five days before a period for at least three cycles in a row, ending within four days of the period starting, and interfering with some normal activities. The Office on Women's Health notes that more than 90 percent of women report some premenstrual symptoms, that as many as three in four say they have had PMS at some point, and that fewer than 5 percent of women of childbearing age have PMDD, the severe form marked by major mood symptoms.
The distinction matters because the response differs. A mild luteal phase is handled with sleep, food, movement and patience. PMS has lifestyle measures with reasonable evidence (ACOG highlights aerobic exercise, complex carbohydrates and 1,200 mg of calcium a day). PMDD is a recognized condition with effective prescription options, including serotonin reuptake inhibitors, and should not be waited out.
ACOG also notes that about half of women seeking help for PMS turn out to have depression or an anxiety disorder, which is present all month and worsens before a period rather than appearing only then. A symptom diary is how the two are told apart. For the full picture, read What Is PMS? Symptoms, Causes and What the Research Says.
When to Talk to a Clinician
The luteal phase is not a reason to see a doctor. These patterns are:
- Mood symptoms before your period that are severe enough to affect work, relationships or how you function, cycle after cycle.
- Any thoughts of harming yourself. In the United States, call or text 988 for the Suicide and Crisis Lifeline.
- Low mood, anxiety or sleep problems that persist through the whole cycle rather than lifting when your period starts.
- Bloating, pelvic pain or bowel changes that are new, worsening, or do not follow your cycle.
Frequently Asked Questions
How long is the luteal phase?
The luteal phase runs from ovulation to the first day of the next period and is usually about 12 to 14 days. In an analysis of more than 600,000 cycles, the mean was 12.4 days with a standard deviation of 2.4 days. It is the more constant half of the cycle; most variation in overall cycle length comes from the follicular phase before ovulation.
Why do I crave carbs before my period?
Energy intake is higher in the luteal phase in most studies, by roughly 150 to 350 kcal a day, and energy expenditure also rises slightly, partly because progesterone raises body temperature. Reviews report more frequent cravings for carbohydrate-rich and fat-rich foods in this phase. One long-standing hypothesis links carbohydrate craving to the brain's serotonin system, which is also implicated in premenstrual mood changes, but this remains a hypothesis with partial support.
Is the luteal phase the same as PMS?
No. The luteal phase is a normal part of every ovulatory cycle, and mild changes in temperature, appetite, sleep and mood are expected. PMS is diagnosed when symptoms appear in the five days before a period for at least three cycles in a row, end within four days of the period starting, and interfere with normal activities. Fewer than 5 percent of women have the severe form, PMDD.
References
Bull, J.R., Rowland, S.P., Scherwitzl, E.B., Scherwitzl, R., Gemzell Danielsson, K. & Harper, J. (2019). Real-world menstrual cycle characteristics of more than 600,000 menstrual cycles. npj Digital Medicine, 2, 83. PMC
Charkoudian, N. & Stachenfeld, N.S. (2014). Reproductive hormone influences on thermoregulation in women. Comprehensive Physiology, 4(2), 793 to 804. PubMed
Shechter, A. & Boivin, D.B. (2010). Sleep, Hormones, and Circadian Rhythms throughout the Menstrual Cycle in Healthy Women and Women with Premenstrual Dysphoric Disorder. International Journal of Endocrinology, 2010, 259345. PMC
Baker, F.C. & Lee, K.A. (2018). Menstrual Cycle Effects on Sleep. Sleep Medicine Clinics, 13(3), 283 to 294. PubMed
White, C.P., Hitchcock, C.L., Vigna, Y.M. & Prior, J.C. (2011). Fluid Retention over the Menstrual Cycle: 1-Year Data from the Prospective Ovulation Cohort. Obstetrics and Gynecology International, 2011, 138451. PMC
Rogan, M.M. & Black, K.E. (2023). Dietary energy intake across the menstrual cycle: a narrative review. Nutrition Reviews, 81(7), 869 to 886. PMC
Tucker, J.A.L., McCarthy, S.F., Bornath, D.P.D., Khoja, J.S. & Hazell, T.J. (2025). The Effect of the Menstrual Cycle on Energy Intake: A Systematic Review and Meta-analysis. Nutrition Reviews, 83(3), e866 to e876. Oxford Academic
Davidsen, L., Vistisen, B. & Astrup, A. (2007). Impact of the menstrual cycle on determinants of energy balance: a putative role in weight loss attempts. International Journal of Obesity, 31(12), 1777 to 1785. PubMed
Schmidt, P.J., Nieman, L.K., Danaceau, M.A., Adams, L.F. & Rubinow, D.R. (1998). Differential behavioral effects of gonadal steroids in women with and in those without premenstrual syndrome. New England Journal of Medicine, 338(4), 209 to 216. PubMed
Yonkers, K.A., O'Brien, P.M.S. & Eriksson, E. (2008). Premenstrual syndrome. The Lancet, 371(9619), 1200 to 1210. PubMed
American College of Obstetricians and Gynecologists (2021, reviewed 2025). Premenstrual Syndrome (PMS). FAQ057. ACOG
Office on Women's Health, U.S. Department of Health and Human Services. Premenstrual syndrome (PMS). womenshealth.gov