Understanding why your cycle is changing, what your body may be telling you, and when it’s time to speak with your doctor.
If your periods have started to feel unpredictable, arriving earlier than expected, skipping a month, or showing up heavier than usual, you may be wondering whether something is wrong. In your 40s, these changes are common. They are often one of the first signs of perimenopause, the transitional phase leading up to menopause.
Perimenopause typically begins in the mid-to-late 40s, though some women notice changes as early as their late 30s. During this transition, your ovaries gradually produce less oestrogen and progesterone, which affects ovulation and the regularity of your menstrual cycle. The result is a period that no longer follows the pattern you may have relied on for decades.
That said, not every period change in your 40s is caused by perimenopause. Thyroid conditions, uterine fibroids, polyps, and other health concerns can also alter your cycle. This guide helps you understand the difference between changes that are a normal part of ageing and those that deserve medical attention.
Is It Perimenopause or Something Else?
Irregular periods in your 40s are most commonly linked to perimenopause, but they can also be caused by other conditions that affect your hormones or reproductive system. The challenge is that several of these conditions share overlapping symptoms, which makes it difficult to identify the cause based on symptoms alone.
The table below outlines the most common causes of irregular periods in your 40s, the typical symptoms associated with each, and the tests your doctor may recommend to confirm or rule out each one.
| Condition | Typical Symptoms | How It Differs from Perimenopause | Tests to Confirm |
| Perimenopause | Irregular cycle length, heavier or lighter flow, hot flushes, night sweats, mood changes, sleep disruption | Symptoms tend to fluctuate and develop gradually over months or years | FSH, oestradiol (limited reliability), symptom tracking over time |
| Thyroid Disorder | Fatigue, weight changes, hair thinning, sensitivity to cold or heat, anxiety or low mood | Symptoms tend to be persistent rather than cyclical. Weight changes may be more pronounced | TSH, free T4, free T3, thyroid antibodies |
| PCOS | Irregular or absent periods, acne, excess facial or body hair, weight gain, difficulty conceiving | Usually present from a younger age. Elevated androgen levels are a distinguishing feature | Testosterone, DHEA-S, LH: FSH ratio, insulin, pelvic ultrasound |
| Uterine Fibroids | Heavy or prolonged periods, pelvic pressure or pain, frequent urination, lower back discomfort | Bleeding is typically heavier rather than irregular in timing. Pelvic pressure is a key indicator | Transvaginal ultrasound, pelvic MRI |
| Uterine Polyps | Irregular bleeding, spotting between periods, bleeding after intercourse, heavier periods | Spotting between periods and post-intercourse bleeding are more characteristic of polyps than perimenopause | Transvaginal ultrasound, saline sonogram, hysteroscopy |
| Stress or Lifestyle Factors | Missed or delayed periods, lighter flow, fatigue, sleep disruption, changes in appetite | Often linked to a specific trigger such as major life change, significant weight loss, or overexercise. Resolves when the trigger is addressed | Clinical assessment. Hormone panel to rule out other causes |
Key point: Many of these conditions can exist alongside perimenopause. For example, you may be perimenopausal and also have a thyroid imbalance or fibroids. If your symptoms are significantly affecting your quality of life, it is worth asking your doctor to investigate rather than assuming everything is perimenopause.
Cycle Pattern Changes to Track
Not every variation in your cycle is a cause for concern. In your 40s, some degree of irregularity is expected. The key is understanding which changes fall within the normal range of perimenopause and which ones may indicate something else.
What Counts as Irregular?
According to the American College of Obstetricians and Gynaecologists (ACOG), a consistent change of seven or more days in your cycle length is an early sign of perimenopause. For example, if your cycle has typically been 28 days and it shifts to 35 days or longer on a regular basis, this variation is considered clinically significant.
Gaps of 60 days or more between periods suggest you may be in the later stages of perimenopause, where ovulation becomes increasingly infrequent.
Common Perimenopausal Cycle Patterns
- Shorter cycles: Your cycle may shorten to 21–24 days, then lengthen. This happens because the follicular phase (the first half of your cycle, before ovulation) gets shorter as your ovaries respond differently to hormonal signals.
- Longer gaps: Cycles of 35–50+ days, or skipping a month entirely, become more common as you progress through perimenopause.
- Heavier flow: Some women experience noticeably heavier periods during perimenopause, sometimes described as flooding. This is often associated with cycles in which ovulation does not occur, leading to a thicker uterine lining.
- Lighter or shorter periods: Other women find that their periods become lighter or last fewer days than they used to.
- Spotting between periods: Light bleeding or spotting outside of your regular period can occur due to hormonal fluctuations.
How to Track Effectively
Keeping a record of your cycle changes helps you identify patterns and gives your doctor useful information if you need an assessment. Track the following each month:
- Start and end date of each period
- Flow level (light, moderate, heavy, or flooding)
- Any spotting between periods
- Associated symptoms such as hot flushes, mood changes, sleep disruption, or pelvic pain
You can use a period tracking app or a simple notebook. The goal is to have a clear record that covers at least three to six months, so your doctor can see trends rather than isolated events.
Tests Your Doctor May Recommend
If you are experiencing irregular periods in your 40s, your doctor may suggest specific tests to understand what is driving the changes. No single blood test can definitively confirm perimenopause. However, testing can help rule out other conditions and provide a clearer picture of your hormonal health.
| Test | What It Measures | Why It’s Useful | When to Test |
| FSH (Follicle-Stimulating Hormone) | The hormone that signals your ovaries to produce eggs | Elevated FSH may suggest your ovaries are working harder to stimulate ovulation, which can indicate perimenopause. However, FSH fluctuates significantly during this transition, so a single reading may not be conclusive. | Day 2–4 of your cycle, if you are still menstruating. Results vary from month to month during perimenopause. |
| Oestradiol (E2) | The primary form of oestrogen produced by the ovaries | Low oestradiol combined with high FSH can support a perimenopause assessment. Very low levels (below 20 pg/mL) are typical of post-menopause. | Day 2–4 of your cycle for the most reliable baseline reading. |
| TSH (Thyroid-Stimulating Hormone) | How well your thyroid gland is functioning | Thyroid disorders can mimic perimenopause symptoms, including irregular periods, fatigue, weight changes, and mood swings. Testing TSH helps rule this out. | Any time. No specific cycle day required. |
| AMH (Anti-Müllerian Hormone) | An indicator of your remaining egg supply, known as ovarian reserve | AMH provides information about where you may be in your reproductive timeline. Very low AMH in your 40s can suggest you are closer to menopause. | Any time. AMH is relatively stable throughout your cycle. |
| Transvaginal Ultrasound | A scan that creates images of the uterus and ovaries using a small internal probe | Helps identify structural causes of irregular bleeding, such as fibroids, polyps, or ovarian cysts. Also allows your doctor to assess the thickness of your uterine lining. | Your doctor will advise on timing based on your symptoms. |
Important: Hormone levels during perimenopause can change significantly from one day or month to the next. Your doctor may recommend repeat testing or rely more heavily on your symptom history and cycle tracking records to assess where you are in the transition.
If you are interested in getting your hormones tested, you can learn more about what each test measures and how to interpret your results in our guide: Hormone Testing for Menopause: What Your Results Mean.
When to See a Doctor
While irregular periods are expected during perimenopause, certain symptoms should not be dismissed. The following are situations where you should speak with your doctor rather than waiting to see if things settle on their own.
Seek Medical Advice If You Experience:
- Periods that last longer than seven days consistently
- Bleeding that is heavy enough to soak through a pad or tampon every hour for several consecutive hours
- Periods occurring less than 21 days apart on a regular basis
- Bleeding or spotting after intercourse
- Any bleeding after you have gone 12 months without a period (post-menopausal bleeding must always be investigated)
- Severe pelvic pain that is not typical for your menstrual cycle
- Significant fatigue, unexplained weight changes, or other symptoms that affect your daily life
These symptoms do not automatically indicate a serious problem. However, they warrant investigation to rule out conditions such as fibroids, polyps, endometrial hyperplasia, or thyroid dysfunction.
Which Specialist Should You See?
Your GP is a good starting point for an initial assessment and basic blood work. If your symptoms are complex or your GP suspects a condition beyond perimenopause, they may refer you to:
- A gynaecologist for structural concerns such as fibroids, polyps, or abnormal bleeding patterns
- An endocrinologist if thyroid or other hormonal conditions are suspected
- A menopause specialist for comprehensive hormonal assessment and treatment planning, particularly if you are considering hormone replacement therapy (HRT)
If you are unsure where to start, you can browse menopause specialists in your area through the Zora Health directory.
Managing Irregular Periods During Perimenopause
If your irregular periods are confirmed to be related to perimenopause, there are several approaches that may help manage your symptoms. The right option depends on the severity of your symptoms, your health history, and your preferences.
Medical Options
- Hormone replacement therapy (HRT): HRT can help stabilise oestrogen levels and may regulate your cycle while also addressing other perimenopause symptoms such as hot flushes, night sweats, and mood changes. Your doctor can discuss whether HRT is suitable for you based on your individual health profile.
- Low-dose oral contraceptives: For some women, low-dose birth control pills can help regulate periods and provide contraception during perimenopause. You can still become pregnant during this transition. These can also help manage heavy bleeding.
- Progestogen therapy: Micronised progesterone or a progestogen-releasing IUD (such as the Mirena) can help manage heavy or prolonged periods by stabilising the uterine lining.
Lifestyle Adjustments
- Regular physical activity: Moderate exercise can help support hormonal balance, improve mood, and reduce the severity of some perimenopause symptoms.
- Stress management: Chronic stress can worsen hormonal fluctuations. Practices such as mindfulness, adequate sleep, and setting realistic boundaries can support your overall well-being during this transition.
- Balanced nutrition: A diet that includes adequate calcium, vitamin D, iron (particularly important if you are experiencing heavy periods), and omega-3 fatty acids can support your body through perimenopause.
Always consult with your healthcare professional before starting any medication or making changes to your treatment plan.
Frequently Asked Questions
Anna Haotanto is the Founder of Zora Health and a passionate advocate for women’s empowerment. Anna’s personal experiences with egg-freezing, PCOS, perimenopause and the challenges of fertility have fueled her mission to provide high-quality information, financing, and support to help women and couples navigate their fertility journeys with confidence. She is also recognised for her achievements in finance, entrepreneurship, and women’s empowerment, and has been featured in various media outlets. You can also follow her on Linkedin or Instagram.
