Miscarriage vs a heavy period: how to tell the difference

There is no reliable way to tell an early miscarriage from a heavy period by looking at the blood alone. What separates them is whether you are pregnant. A heavy period is a menstrual period that is heavier than you would like or than usual. A miscarriage is the loss of a pregnancy before 24 weeks, according to the NHS, and in the earliest weeks it can come with bleeding that you may mistake for a late, heavy period.

If there is any chance you could be pregnant, for example your period is late, you have had a positive pregnancy test or you have symptoms of early pregnancy, treat bleeding as something to discuss with a clinician rather than as a period. If you know you are not pregnant, the information on heavy periods applies, and the NHS says heavy periods may be normal for you and do not always need treatment.

The NHS says you may have heavy periods if you need to change your pad or tampon every 1 to 2 hours, need to use two types of product together, have periods lasting more than 7 days, pass blood clots larger than about 2.5cm (the size of a 10p coin), bleed through to your clothes or bedding, avoid daily activities because of your periods or feel tired or short of breath a lot. It says heavy periods can be normal and sometimes occur when you first start periods, after pregnancy or approaching menopause.

For miscarriage, the NHS lists spots of pink, red or brown blood (spotting), larger areas of blood that may need a period pad (light bleeding) and red blood that soaks through a pad (heavy bleeding). Other symptoms can include pain and cramping in the lower tummy, pink, grey or white lumps coming out of the vagina that may look or feel stringy, and fluid suddenly coming out.

The table sets out the features described by the NHS. Several rows overlap, which is why the question is a common one.

If a doctor thinks you might be having a miscarriage, the NHS says you will be asked questions about your pregnancy, any previous pregnancies and your general health, and may be offered blood tests or urine tests and an internal vaginal (trans-vaginal) ultrasound scan to check your pregnancy. This is how a miscarriage is distinguished from other causes of bleeding, including bleeding that does not mean the pregnancy is lost.

For heavy periods, the NHS says a GP may arrange blood tests to check for underlying conditions such as iron deficiency anaemia, and may refer you for tests or to a specialist if treatment does not work or a condition may be the cause. Conditions that can be behind heavy periods include polyendocrine metabolic ovarian syndrome (PMOS, formerly PCOS), fibroids, endometriosis, adenomyosis and pelvic inflammatory disease, bleeding disorders such as Von Willebrand disease and some medicines. Rarely, heavy periods can be a sign of womb cancer.

If you are pregnant and bleeding, the NHS says to get urgent medical help if you have light vaginal bleeding or spotting with no or only mild tummy pain, or if you have unusual discharge or fluid leaking from the vagina. Call your maternity unit if you have the number, or an early pregnancy unit if you are less than 20 weeks pregnant. If you cannot contact one, call NHS 111.

Call 999 if you are pregnant, have vaginal bleeding and have severe tummy pain (so bad you cannot do daily tasks or focus on a book or television), pain in your shoulder, feel sick, faint or dizzy or lose consciousness, or the bleeding is heavy and soaks a period pad soon after you put it on. These can be signs you need immediate treatment.

If you are not pregnant, the NHS says to see a GP if heavy periods are affecting your life, you have had them for some time, you have severe pain during periods, you bleed between periods or after sex, or you have heavy periods with other symptoms such as pain when peeing, pooing or having sex.

The NHS says a miscarriage cannot be stopped once it has started and that options depend on your symptoms and how many weeks pregnant you are. In early miscarriage before 14 weeks this may mean waiting for symptoms to pass, taking medicine, or a procedure under general or local anaesthetic. After a miscarriage you may have tummy pain for a few days and bleeding or spotting for up to 2 weeks, and a period can return within about 8 weeks. The NHS says everyone experiences miscarriage differently and that counselling and support are available. If you have had 3 or more miscarriages, talk to a GP, who can arrange tests.