Perimenopause vs Pernicious Anaemia: Spot the Difference

Two Conditions With Surprisingly Similar Symptoms

Perimenopause and pernicious anaemia are both more common in middle-aged women and both produce a cluster of symptoms that can be mistaken for stress, burnout, or depression. Fatigue, brain fog, low mood, sleep disturbance, and poor concentration appear in both, which means that pernicious anaemia is sometimes hidden behind a perimenopause diagnosis for months or even years. Pernicious anaemia is an autoimmune condition in which the stomach fails to produce enough intrinsic factor, a protein needed to absorb vitamin B12 from food. Without adequate B12, the body cannot make healthy red blood cells and the nervous system begins to suffer. Because B12 deficiency develops gradually, the early symptoms are easy to attribute to the hormonal changes of midlife.

How Pernicious Anaemia Develops

In pernicious anaemia, the immune system attacks the parietal cells of the stomach lining, reducing or eliminating production of intrinsic factor. Without intrinsic factor, dietary B12 cannot be absorbed in the small intestine regardless of how much is consumed in food. Vitamin B12 stores in the liver can last several years, so the deficiency often builds slowly before symptoms become obvious. It tends to run in families and is associated with other autoimmune conditions including Hashimoto's thyroiditis, type 1 diabetes, and vitiligo. Women are diagnosed with pernicious anaemia more often than men, and the peak age of onset overlaps with the perimenopause years. This demographic overlap makes the two conditions particularly easy to confuse.

Symptoms That the Two Conditions Share

Fatigue is the dominant symptom in both conditions. In perimenopause it is driven by poor sleep, hormonal fluctuations, and the metabolic changes of declining oestrogen. In pernicious anaemia it comes from impaired red blood cell production and nervous system dysfunction. Brain fog, described as difficulty concentrating, slow thinking, and a sense of mental cloudiness, is a core complaint in both. Low mood and mild depression feature in each condition. Pale skin can accompany anaemia of any cause, and changes in skin quality also occur in perimenopause. Heart palpitations can arise from anaemia as the heart works harder to compensate for fewer functional red blood cells, and they also appear during the perimenopause transition. Breathlessness on exertion is another shared complaint.

Symptoms That Are More Specific to Pernicious Anaemia

Neurological symptoms are the clearest distinguishing feature of B12 deficiency and do not occur in perimenopause alone. These include tingling or numbness in the hands and feet, often described as pins and needles, which reflects damage to peripheral nerves. Balance problems and difficulty walking steadily can develop as the condition progresses and affects the spinal cord in a process called subacute combined degeneration. A smooth, sore, red tongue, known as glossitis, is a classic sign of B12 deficiency. Yellowing of the skin or eyes can occur because poorly formed red blood cells break down more rapidly. Mouth ulcers that recur frequently and a reduced appetite with unintended weight loss are also more characteristic of B12 deficiency than perimenopause.

Symptoms That Are More Specific to Perimenopause

Vasomotor symptoms are the hallmark of perimenopause and are absent in pernicious anaemia. Hot flashes, night sweats, and the sudden wave of heat through the body are driven by falling oestrogen and represent one of the most reliable indicators of the menopause transition. Irregular menstrual cycles, changes in flow, and eventually the cessation of periods mark perimenopause in a way that has nothing to do with B12 status. Vaginal dryness and urinary changes associated with genitourinary syndrome of menopause are also specific to the perimenopause experience. Joint stiffness and breast tenderness that track with the cycle point toward hormonal change rather than nutritional deficiency.

How Doctors Test for Each

Treatment and Symptom Tracking

Pernicious anaemia is treated with regular B12 injections, usually given every three months in the UK once stores are repleted, because oral B12 cannot be absorbed without intrinsic factor. Neurological symptoms respond more slowly than haematological ones, and some women notice a significant improvement in energy and mental clarity within weeks of starting treatment. Perimenopause is managed with lifestyle changes and, for many women, hormone therapy. The two conditions can coexist, and receiving a diagnosis of perimenopause does not rule out a B12 problem. Tracking your symptoms over time, noting when fatigue is worst, whether you have any tingling, and how your mood and concentration change day to day, gives you richer information to share with your doctor. PeriPlan lets you log symptoms and track patterns over time, which can make a real difference when trying to untangle overlapping conditions.