You had a period at the start of the month, and now there’s another one before the month is out. It feels like too many. Most of the time it isn’t, and you can usually tell which case you’re in by counting days.
Is it normal to have two periods in one month?
Often it is. The NHS says periods usually come around every 28 days, and that anything from every 21 days to every 35 days is common. A calendar month is 30 or 31 days long, so any cycle shorter than that will sometimes fit two periods into one month.
Here’s how that looks with a 24-day cycle. If your period starts on October 2nd, the next one starts on October 26th. That’s two periods in October and a perfectly ordinary cycle. Even a 28-day cycle gives you 13 periods a year, one more than there are months, so about once a year one month gets two.
Count the days between periods, not the month
Your cycle runs from the first day of one period to the day before the next one starts. The NHS counts it that way. What matters is the number of days between the two first days, and the month they fall in tells you nothing.
Put your last few start dates into the cycle length calculator and it lists every gap. If the gap is 21 days or more and both bleeds were your usual flow, you had two normal periods that landed in the same month. The guide to normal menstrual cycle length explains the range in more detail.
When the gap is shorter than 21 days
That’s a short cycle. The NHS calls periods irregular when the gap between them is less than 21 days or more than 35. The American College of Obstetricians and Gynecologists lists cycles shorter than 21 days as abnormal uterine bleeding. That label sounds worse than it is. It means a doctor should find the cause, not that something is wrong.
The NHS lists these as common causes of irregular periods.
- The first years after periods start. Cycles take a while to settle.
- Perimenopause. The NHS says a change to your periods is usually one of the first signs, and they may come more often or less often. ACOG says that in your 40s the days between periods may increase or decrease. The perimenopause guide covers what to track.
- Hormonal contraception. The NHS names the progestogen-only pill, the contraceptive injection and the hormonal coil (IUS).
- Losing or gaining a lot of weight, stress and anxiety, and exercising too much.
- Conditions like PCOS or thyroid problems. The NHS now calls PCOS polyendocrine metabolic ovarian syndrome (PMOS). Our PCOS guide has more.
One short cycle after a bad month isn’t much to go on. Several in a row, or a pattern that’s changed from what you’re used to, is what to take to a GP.
Was the second bleed really a period?
This is the question to settle first. Spotting and other bleeding between periods can look like a period, especially when it lasts a day or two. Spotting is light, often brown or pink, and doesn’t need a pad or tampon. A period is your usual flow.
If the second bleed was much lighter or shorter than your normal period, it was probably something else. The common causes are breakthrough bleeding on hormonal contraception, polyps or fibroids, and infections such as chlamydia. The guide to bleeding between periods goes through them. A doctor should check that kind of bleeding even when it’s light.
Pregnancy can cause bleeding too. The NHS describes implantation bleeding as a bleed similar to a very light period, with spotting or only a little blood, around the time your period is due. If you could be pregnant and the bleed wasn’t your usual period, take a test.
When to see a GP
The NHS says to see a GP if any of these apply.
- Your periods are irregular, or your usual pattern changes.
- Your periods last longer than 7 days.
- You have bleeding between periods.
- You have irregular periods along with weight gain, tiredness, hair growth on your face, or dry or oily skin.
- Your periods are irregular and you’re struggling to get pregnant.
Don’t wait for a routine appointment if you’ve missed a period and now have unusual bleeding with pain in your abdomen. The NHS says to ask for an urgent GP appointment or call 111, because it can be a sign of an ectopic pregnancy. ACOG says to get emergency care if you soak through a pad or tampon every hour for more than two hours and feel dizzy, lightheaded or short of breath, or have chest pain.
Take your dates with you. ACOG asks for the dates, length and type of each bleed, meaning light, medium, heavy or spotting. A period diary or an app gives you that record without relying on memory.
How Plum helps you tell the difference
We make Plum, a period tracker for iPhone, so here’s what it does with a month like this. You log a period day with a tap, and you can log spotting as spotting, so a light bleed doesn’t get counted as a new cycle. From the periods you log, Plum works out your average cycle and how much it varies, and it shows you both for free. A short cycle shows up as a number rather than a hunch.
Plum won’t tell you why a cycle was short. That takes a GP. It does give you the dates they’ll ask for. Plum shows no ads and never sells personal data.
