What blood tests should you order during perimenopause?

One of the most common things I hear from women in their late 30s, 40s and early 50s is:

“My doctor said everything was normal… but I still feel awful.”

They’re exhausted before the day even starts. Foggy headed. Waking at 3am. Gaining weight around the middle despite eating the same way they always have. Flat, anxious, inflamed, overwhelmed or simply feeling unlike themselves.

Common symptoms women notice during perimenopause can include:

• fatigue and low motivation

• brain fog and poor concentration

• weight gain around the middle

• waking during the night

• increased anxiety or mood changes

• cravings and blood sugar swings

• heavier or irregular periods

• hair thinning and poor recovery

  
  

Many women start wondering what blood tests should you order during perimenopause when these symptoms begin affecting their energy, sleep, mood and ability to feel like themselves again. Often, they’ve already had blood tests done. Sometimes multiple times. But many of the early hormonal and metabolic changes that occur during perimenopause do not always show up clearly when we are only looking for disease (a).

This is where deeper bloodwork interpretation can become incredibly valuable.

While there is no single blood test that “diagnoses” perimenopause, bloodwork can provide useful insight into how the body is coping during this transition. It can help uncover patterns relating to blood sugar regulation, thyroid function, nutrient status, inflammation and energy production; all areas that commonly contribute to symptoms women experience during midlife.

Can blood tests confirm perimenopause?

Not reliably.

Perimenopause is primarily diagnosed through a combination of symptoms, age, menstrual cycle changes and clinical patterns over time. Hormones fluctuate significantly during this stage of life, sometimes changing dramatically even within the same month. Because of this, a single estrogen or progesterone test often does not provide the full picture (a).

This is why many women are told:

“Your hormones are normal.”

…despite feeling very far from normal.

Rather than focusing on one isolated hormone result, I prefer to assess the broader physiological picture. How is the body managing stress? Is blood sugar becoming more unstable? Is thyroid function optimal? Are nutrient deficiencies contributing to symptoms? Are inflammatory or metabolic changes beginning to emerge?

These shifts can begin years before menopause itself and often explain why women suddenly feel like their body has changed overnight.

Fasting insulin and HbA1c

One of the most important blood tests for perimenopause and metabolic health is assessing blood sugar regulation.

As estrogen changes during perimenopause, insulin sensitivity can decline. This can contribute to abdominal weight gain, increased cravings, fatigue, brain fog, energy crashes and difficulty losing weight despite doing “all the right things (b).”

HbA1c provides an average picture of blood sugar over the previous two to three months, while fasting insulin can reveal earlier metabolic strain before glucose levels become abnormal. I often see women with completely “normal” glucose and HbA1c results but significantly elevated fasting insulin levels (c).

This matters because insulin resistance can begin years before type 2 diabetes develops. In many cases, symptoms are already appearing long before pathology ranges flag anything concerning.

Thyroid function testing

Many symptoms associated with thyroid dysfunction overlap heavily with perimenopause. Fatigue, hair thinning, low mood, constipation, brain fog, weight gain and feeling cold can all be linked to thyroid health (d).

A standard thyroid screen often only includes TSH, however a broader thyroid picture can sometimes provide more meaningful insight. Depending on the person and their symptoms, this may include:

• TSH

• Free T4

• Free T3

• thyroid antibodies such as TPO and TgAb

I regularly see women with symptoms suggestive of Hashimoto’s thyroiditis who have previously been told their thyroid is “fine.” Autoimmune thyroid conditions become increasingly common in midlife women, which makes this an important area to investigate thoroughly.

Iron studies and ferritin

Low iron is one of the most overlooked causes of fatigue in women. It can contribute to poor exercise tolerance, hair loss, dizziness, low motivation, restless legs and feeling exhausted despite adequate sleep. Heavy or irregular periods during perimenopause can significantly affect iron stores, even before menopause itself.

Ferritin is particularly important because women can have haemoglobin levels within range while still having depleted iron reserves. Equally, ferritin that is too high may also provide clues around inflammation, liver stress or metabolic dysfunction. This is why context matters so much when interpreting bloodwork.

Vitamin D

Vitamin D plays an important role in immune health, bone density, muscle function, mood, insulin sensitivity and inflammation regulation (e).

As estrogen declines during perimenopause, maintaining bone and muscle health becomes increasingly important. Low vitamin D is extremely common in New Zealand women, particularly through winter or in women spending most of their time indoors. Optimising vitamin D status can be an important part of supporting long-term health, energy and resilience during midlife; it's not just about protecting your bones.

Vitamin B12 and folate

Vitamin B12 and folate are essential for nervous system function, energy production, cognition and red blood cell formation.

Low levels may contribute to symptoms such as fatigue, poor concentration, brain fog, tingling sensations and low mood. This becomes particularly relevant in women dealing with chronic stress, digestive issues, restrictive eating patterns or medications that may impair nutrient absorption.

These nutrients are often overlooked, yet they can have a significant impact on how someone feels day to day.

CRP and inflammatory markers

Low-grade inflammation is increasingly recognised as a contributor to fatigue, metabolic dysfunction, cardiovascular disease and mood changes.

Markers such as CRP can provide insight into the body’s overall inflammatory load. Stress, poor sleep, blood sugar instability, excess visceral fat, gut dysfunction and nutrient deficiencies can all contribute to ongoing inflammation.

Looking at these markers alongside the wider clinical picture can help identify areas where the body may be under strain long before disease develops.

What about estrogen, progesterone and cortisol testing?

These tests can sometimes be useful, however context is important.

Hormone levels fluctuate significantly throughout perimenopause, which means isolated hormone testing can occasionally create more confusion than clarity. While there are situations where hormone testing is appropriate, I am often more interested in the broader patterns driving symptoms; things like blood sugar regulation, stress physiology, inflammation, thyroid function, sleep quality and nutrient status. These are often the areas having the biggest day-to-day impact on how women actually feel.

Why “normal” blood tests don’t always explain your symptoms

One of the most frustrating experiences for many women in perimenopause is being told their blood tests are “normal” despite clearly not feeling well.

Standard pathology ranges are designed primarily to identify disease or serious dysfunction. They are incredibly important from a medical perspective, but they are not always designed to detect earlier physiological changes that may already be affecting energy, mood, metabolism or hormone function. This is why women can experience symptoms long before a result falls outside the standard reference range.

A more functional interpretation of bloodwork looks at:

• patterns and trends over time

• relationships between markers

• symptom presentation

• lifestyle and stress load

• sleep, nutrition and metabolic health

• the bigger physiological picture

...rather than viewing each marker in isolation.

For example, someone may technically have a “normal” HbA1c while already showing elevated fasting insulin levels. Another woman may sit within the reference range for ferritin while still experiencing symptoms consistent with low iron stores. Thyroid markers may appear acceptable on paper, yet the broader pattern suggests the thyroid is under stress.

The numbers matter, but so does the bigger physiological picture.

Final thoughts

Perimenopause is not “just ageing.”

It is a significant hormonal and metabolic transition that affects nearly every system in the body including the brain, metabolism, sleep, muscles, bones, cardiovascular system and nervous system (a),(b).

And while there is no single blood test that confirms perimenopause, the right bloodwork can provide valuable insight into why you feel the way you do and what your body may need support with.

If you’re feeling exhausted, inflamed, foggy, struggling with weight changes or simply feel like your body has changed in ways you do not understand, deeper bloodwork interpretation can often help connect the dots.

You can read more about common symptoms and metabolic changes during perimenopause here or explore support options via the Services page.

References

(a) Santoro N, Epperson CN, Mathews SB. Menopausal symptoms and their management. Endocrinol Metab Clin North Am. 2015;44(3):497-515. doi:10.1016/j.ecl.2015.05.001

(b) De Paoli M, Zakharia A, Werstuck GH. The role of estrogen in insulin resistance. Am J Pathol. 2021;191(9):1490-1498. doi:10.1016/j.ajpath.2021.05.011

(c) American Diabetes Association Professional Practice Committee. Standards of care in diabetes. Diabetes Care. 2024;47(Suppl 1):S1-S321.

(d) Kaur J, Goyal G, Avula A. Hashimoto Thyroiditis. In: StatPearls. StatPearls Publishing; 2025.

(e) Holick MF. Vitamin D deficiency. N Engl J Med. 2007;357(3):266-281. doi:10.1056/NEJMra070553