Perimenopause
Is it perimenopause or something else?
Quick answer
Many perimenopause symptoms, such as tiredness, low mood, brain fog, weight change and poor sleep, also have other common causes in midlife, including an underactive thyroid, low iron, depression and medicine side effects. Perimenopause is more likely when symptoms come with changing periods, hot flashes or night sweats, and when they rise and fall over weeks. A doctor can check for other causes with simple blood tests when the picture is unclear. Tracking which symptoms move together gives them a head start.
What might be happening
Perimenopause touches so many systems that it overlaps with plenty of other conditions. An underactive thyroid, for example, can cause tiredness, weight gain, feeling cold, constipation, low mood and trouble concentrating, according to NHS guidance. Low iron, often from heavy periods, causes tiredness and breathlessness. Depression and anxiety can cause poor sleep and brain fog on their own.
NICE guidance says that for women over 45, perimenopause can usually be diagnosed from symptoms and period changes without hormone tests, but that tests such as thyroid function or a blood count can be used when another cause is suspected. In other words, the question is rarely "which one is it?" in isolation, and more often "what else could be adding to this?"
The pattern over time is a strong clue. Perimenopause symptoms tend to fluctuate, cluster with cycle changes and hot flashes, and vary month to month. Thyroid symptoms tend to build steadily. Depression tends to bring persistent low mood and loss of interest regardless of the cycle. Several causes can also be present at once, which is common in midlife.
What to notice
- Whether your periods are changing in length, flow or predictability.
- Hot flashes or night sweats, which point towards perimenopause.
- Whether symptoms fluctuate week to week or build steadily.
- Feeling cold, constipation, or dry skin and hair (thyroid clues).
- Breathlessness, a racing heart or pale skin with heavy periods (iron clues).
- Low mood and loss of interest most days, whatever your cycle is doing.
- Any new medicines or changes in dose.
A few weeks of notes on these signals helps a doctor decide which tests, if any, are worth doing.
Related patterns
Conditions that commonly overlap with perimenopause symptoms include:
- underactive thyroid
- iron deficiency, often with heavy periods
- depression and anxiety
- side effects from medicines or contraception
- sleep problems with their own cause
Having one of these does not rule out perimenopause. Treating both often makes the biggest difference.
Notice the pattern
Because so many midlife symptoms overlap, it is easy for either perimenopause or another condition to be missed. Women are sometimes told their symptoms are "just stress" or "just your age" when a treatable cause is present.
A clear record showing which symptoms travel with your cycle and hot flashes, and which follow their own path, helps a doctor see both possibilities at once and decide what to check.
When to get support
Speak to a doctor if:
- tiredness, low mood or brain fog have lasted more than a few weeks
- you have heavy periods with tiredness or breathlessness
- you are gaining or losing weight without a clear reason
- you have low mood or loss of interest most days
- you are under 45 and your periods have changed
Ask which other causes might fit your symptoms and whether any tests are needed. If you ever have thoughts of harming yourself, contact your local emergency services or a crisis line in your country.