∞ Your cycle and the scale

Do you gain weight on your period? Why it happens, and when it goes

Yes, many women weigh more in the days before and during their period, but it is water, not fat. In one study that weighed women twice a week, weight was on average about half a kilo higher during their period, almost all of it extra fluid; some women notice a kilo or two. It usually eases over the first days of your period and is gone by about a week after it starts.

By the Turtle Method team · Updated 7 October 2026 · Sources: 6 studies and guidelines, listed below

Key facts

Weight gain around a period is mostly fluid, not fat. In a study of 42 women weighed twice a week, body weight was about 0.45 kg higher during menstruation, and extracellular water rose by about 0.47 kg. In 765 cycles of daily diaries, self-reported fluid retention peaked on the first day of the period and was lowest in the mid-follicular phase, roughly a week later.

Do you gain weight on your period?

Most women do, a little, and it is one of the most common reasons a good week suddenly looks like a bad one on the scale. What goes up is water, not body fat. Gaining even half a kilo of real fat in a few days would take far more extra food than anyone eats before a period, and the rise disappears on its own once your period gets going.

The average change is smaller than many women expect. In a Greek study that measured 42 women twice a week across a cycle, weight was about 0.45 kg higher during their period, and nearly all of that difference was extracellular water, the fluid that sits outside your cells. Fat mass did not change. Averages hide a wide spread, though: plenty of women see a kilo or two, and a few see more, especially if they also feel bloated or constipated or are eating saltier food that week.

So if you are asking "is 3 kg of weight gain before my period normal?", a jump that size is unusual but it is still very unlikely to be fat. Watch what happens over the following week. If it does not come back down, something else is going on, and that is worth looking at.

Why you gain weight before your period

Your hormones do more than run your cycle. Oestrogen and progesterone also shift the set points your body uses to manage fluid, thirst and blood volume, so how much water you hold can change from week to week. In the second half of the cycle, the luteal phase, several things tend to stack up:

• Fluid retention. In a year-long diary study of 62 healthy women, self-reported fluid retention rose through the second half of the cycle and peaked on the first day of the period.
• Bloating and slower digestion. The NHS lists bloating among the most common premenstrual symptoms, and a fuller gut weighs more.
• Appetite and cravings. Changes in appetite and food cravings are also common. Saltier and more carbohydrate-rich food can make your body hold on to more water, so the scale can rise even when you have not eaten much more.
• Your metabolism. Resting metabolism may tick up slightly in the luteal phase, but the effect is small and was not statistically clear in newer studies, so it does not change the picture much.

None of this is your body going wrong. It is your body doing exactly what it is designed to do, and it resets every month.

What the scale does across your cycle

Perioddays 1–5Folliculardays 6–13Ovulationdays 14–15Lutealdays 16–23Late lutealdays 24–28

• Period · days 1–5Weight and bloating are often highest on day 1, then start to fall over the next few days.
• Follicular · days 6–13Fluid is usually at its lowest around the middle of this phase. Often your lightest week.
• Ovulation · days 14–15Fluid retention starts to rise over the days around ovulation.
• Luteal · days 16–23Fluid retention starts to build. Appetite may be higher.
• Late luteal · days 24–28The premenstrual week: bloating, cravings and the scale often creep up towards your period.

Day numbers are an example. Cycles of 21 to 35 days are normal, and the pattern varies a lot between women and from month to month.

When does period weight go away?

For most women the extra weight starts to drop within the first few days of the period. In the diary study above, fluid retention was highest on the first day of bleeding and lowest in the middle of the follicular phase, which in a 28-day cycle is roughly a week after your period starts. So by the end of your period, or a few days after, you will usually be back to your normal weight.

How long does period bloating last? The same pattern applies. Bloating usually builds in the days before your period, peaks around day 1 and eases over the next few days. If you want to know your own timing, weigh yourself at the same time each morning for two or three cycles and note your period dates. Most women find their pattern repeats.

How to read the scale around your period

The scale is one signal, not the signal. A few habits stop a premenstrual jump from knocking you off course:

• Compare like with like. Put this month's premenstrual week next to last month's, not next to the week after your period.
• Look at the weekly average, not one morning. A rolling average smooths out water. See why your weight can jump overnight.
• Log your period. When your period dates sit next to your weight, a luteal-phase rise stops being a surprise. Here is how to log a period in Turtle.
• Don't cut food harder that week. There is no fat to lose here, so eating less only makes the week harder. The NHS suggests that frequent smaller meals, every 2 to 3 hours, may help with premenstrual symptoms.
• Keep training if you feel up to it. Regular exercise is one of the things the NHS suggests for premenstrual symptoms. A walk counts.

For more on what each phase does, read the menstrual cycle phases and luteal phase symptoms.

Know your own pattern

See your cycle and your weight side by side

Log your period in Turtle and see how your weight moves across your own cycle, so a luteal-phase jump stops being scary.

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When it is not your period

If your weight stays up after your period, or keeps climbing over several cycles, water is no longer the likely answer. Our guide to why you might not be losing weight walks through the usual causes, from sleep to how much you are really eating.

When to see your GP: See your GP if your premenstrual symptoms affect your daily life, your periods change a lot, or you notice swelling or weight gain that does not settle after your period.

What the research says

Each study below was checked against its PubMed record, or read at source for NHS, NICE and government pages, on 7 October 2026.

1. In 42 women measured twice a week, body weight was about 0.45 kg higher during menstruation than in the first week of the cycle, matched by a 0.47 kg rise in extracellular water. No other body composition changes were significant.

   Kanellakis S, Skoufas E, Simitsopoulou E, et al. (2023). Changes in body weight and body composition during the menstrual cycle. American journal of human biology : the official journal of the Human Biology Council. 35(11):e23951 doi.org/10.1002/ajhb.23951

2. In 765 cycles of daily diaries from 62 healthy women, self-reported fluid retention was lowest in the mid-follicular phase, rose around ovulation and peaked on the first day of menstrual flow.

   White CP, Hitchcock CL, Vigna YM, et al. (2011). Fluid Retention over the Menstrual Cycle: 1-Year Data from the Prospective Ovulation Cohort. Obstetrics and gynecology international. 2011:138451 doi.org/10.1155/2011/138451

3. A review of how oestrogen and progesterone affect fluid regulation: they alter the set points for thirst, the water-retaining hormone vasopressin and plasma volume, while total body water and sodium change only mildly.

   Stachenfeld NS (2008). Sex hormone effects on body fluid regulation. Exercise and sport sciences reviews. 36(3):152-9 doi.org/10.1097/JES.0b013e31817be928

4. Across 26 studies, resting metabolic rate was slightly higher in the luteal phase, but in studies published since 2000 the difference was smaller and not statistically significant.

   Benton MJ, Hutchins AM, Dawes JJ (2020). Effect of menstrual cycle on resting metabolism: A systematic review and meta-analysis. PloS one. 15(7):e0236025 doi.org/10.1371/journal.pone.0236025

5. In 612,613 app-tracked cycles, the average cycle was 29.3 days and the luteal phase averaged 12.4 days. The study was funded by the app maker, Natural Cycles.

   Bull JR, Rowland SP, Scherwitzl EB, et al. (2019). Real-world menstrual cycle characteristics of more than 600,000 menstrual cycles. NPJ digital medicine. 2:83 doi.org/10.1038/s41746-019-0152-7

6. The NHS lists bloating, breast tenderness, appetite changes and cravings among the common premenstrual symptoms, suggests regular exercise and a symptom diary, and advises seeing a GP if symptoms affect daily life.

   NHS. PMS (premenstrual syndrome). NHS website. Accessed 7 October 2026. www.nhs.uk/conditions/pre-menstrual-syndrome/

Questions women ask

This guide is general information, not medical advice. It isn't tailored to you and doesn't replace advice from your GP or another qualified professional. If something's worrying you, speak to your GP. LeanShield™ is a trademark of ParrotPal Ltd: it rates the habits linked to protecting muscle, is not a medical device and doesn't measure muscle.