PCOS Fatigue Blood Tests: What to Test When You’re Exhausted All the Time (and Why Results Are Often Missed)

PCOS Fatigue Blood Tests: What to Check (So You Can Stop Guessing and Start Getting Answers)

If you have PCOS and feel exhausted all the time, it’s easy to start questioning yourself.

You might be told:

• “That’s normal.”

• “You’re probably just stressed.”

• “Try sleeping more.”

• “It’s part of PCOS.”

But persistent fatigue isn’t something you should just accept, especially when it’s affecting your motivation, mood, productivity, training, parenting, relationships, and ability to feel like yourself.

One of the most important steps in addressing PCOS fatigue is making sure the right testing has been done.

Because fatigue is not a diagnosis — it’s a symptom.

Woman sleeping in a chair

Why Testing Matters for PCOS Fatigue

PCOS fatigue is rarely caused by one single issue.

It’s often a combination of:

• insulin resistance and blood sugar instability

• thyroid dysfunction

• nutrient depletion

• inflammation

• cortisol dysregulation

• poor sleep (including sleep apnea)

This is why women can spend years feeling exhausted while being told everything looks fine.

Often, the right markers haven’t been tested or they’ve been tested but not interpreted through the lens of PCOS and metabolic health.

The 10 Most Important Tests to Investigate PCOS Fatigue

1) Iron Studies + Ferritin

This is one of the biggest causes of fatigue — especially in women, and especially postpartum or with heavy periods.

Ask for:

• ferritin

• serum iron

• transferrin

• transferrin saturation

• TIBC

Why it matters:Low ferritin can cause fatigue even when haemoglobin is “normal.”

If ferritin is low, it also impacts:

• thyroid function

• mood and motivation

• hair growth

• training performance and recovery

2) Full Blood Count (FBC)

A full blood count helps identify:

• anemia

• infection or immune stress

• general red blood cell health

Fatigue without checking FBC is incomplete.

3) Thyroid Function (Not Just TSH)

The thyroid is one of the most overlooked drivers of fatigue, weight changes, brain fog and mood disruption.

Ask for:

• TSH

• free T4

• free T3

Depending on symptoms/history, also consider:

• thyroid antibodies (TPO-Ab and TgAb)

TSH alone is often not enough to explain fatigue patterns.

4) Vitamin D

Vitamin D influences immune health, inflammation, mood, energy and hormone pathways.

Ask for:

• 25-OH vitamin D

Low vitamin D is extremely common in women with chronic inflammation, fatigue and hormone issues.

5) Vitamin B12 + Folate

These are essential for:

• energy production

• nervous system function

• red blood cell formation

• cognitive performance

Ask for:

• B12

• folate

Deficiency can show up as:

• fatigue

• anxiety

• brain fog

• numbness/tingling

• low motivation

6) Magnesium (Best Marker When Accessible)

Magnesium is involved in hundreds of processes, including:

• stress response

• sleep quality

• insulin sensitivity

• muscle recovery

Serum magnesium isn’t always reliable, but if available, consider:

• RBC magnesium

Magnesium depletion is common in high stress states and insulin resistance.

7) Fasting Insulin + Glucose + HbA1c

This one is absolutely critical for PCOS fatigue.

Many women are told their glucose is “normal,” but insulin resistance can still be present.

Ask for:

• fasting insulin

• fasting glucose

• HbA1c

Why it matters: Blood sugar swings and high insulin levels can cause:

• energy crashes

• cravings

• brain fog

• feeling flat and unmotivated

• poor sleep and inflammation

8) Lipids / Cholesterol Panel

This isn’t just for heart health — it can show deeper metabolic patterns.

Ask for:

• total cholesterol

• LDL

• HDL

• triglycerides

In PCOS, metabolic strain and insulin resistance often show up here too.

9) Inflammation Markers

Inflammation is a common driver of fatigue in PCOS and can make the body feel heavy, foggy and depleted.

Ask for:

• hs-CRP

• ESR (if indicated)

This can help confirm whether chronic inflammation is contributing to fatigue.

10) Liver Function

The liver plays a major role in:

• hormone clearance

• blood sugar regulation

• inflammation load

• nutrient storage

Ask for:

• ALT

• AST

• GGT

Fatty liver changes are more common in insulin resistance patterns and can absolutely contribute to fatigue.

Optional Tests Depending on Symptoms

Not everyone needs these, but they can be helpful depending on your history:

• cortisol testing (especially if “wired but tired,” insomnia, anxiety)

• DHEA-S (stress hormone marker)

• coeliac screening (if gut symptoms or low iron)

• sleep apnea investigations (especially if waking unrefreshed, snoring)

• sex hormone patterns (especially low progesterone, poor ovulation)

Why You Can Feel Exhausted Even If “Results Are Normal”

This is one of the most frustrating experiences for women.

Pathology ranges are designed to detect disease — not to reflect optimal levels or how you feel.

So you may be “in range” but still depleted or dysfunctional.

Also, single markers without context can be misleading.For example:

• normal glucose but elevated insulin

• “normal TSH” but low T3

• “normal iron” but low ferritin

• normal haemoglobin but low B12

That’s why results should always be interpreted alongside:

• symptoms

• cycle patterns

• metabolic health

• stress load and sleep quality

What to Do With Your Results

Testing is step one.

The goal is to use results to build a plan that:

• improves insulin sensitivity

• corrects deficiencies

• reduces inflammation

• supports thyroid function if needed

• improves sleep and stress resilience

Fatigue often begins improving once the true driver is supported properly.

Final Thoughts

If you have PCOS and you’re feeling exhausted all the time, you deserve more than vague reassurance.

The right tests can identify what’s driving your fatigue and give you real direction.

You do not have to live in survival mode.

If you’re struggling with PCOS fatigue and you don’t know what blood tests to ask for (or how to interpret your results), I can help.

Book a FREE Naturopathic PCOS Assessment Call and we’ll map out what’s driving your fatigue, what testing should be prioritised, and the most supportive next steps to restore energy, hormone balance and metabolic health.