Always tired? The four tests worth doing first

Fatigue has a short list of common, treatable causes. These are the tests that separate them.

Persistent tiredness is the single most common reason people book a blood test, and one of the hardest symptoms to pin down — because almost everything causes it. The useful news is that a small number of common, treatable causes account for a large share of cases, and four tests separate most of them.

1. Anaemia

A complete blood count is the first test for a reason. Low haemoglobin means less oxygen reaching your tissues, which produces exactly the tiredness, breathlessness on stairs and general flatness people describe.

The CBC also hints at the cause. Small, pale red cells point towards iron deficiency; large ones point towards B12 or folate.

2. Iron deficiency without anaemia

Here is the part that catches people out: you can be iron deficient and still have a normal haemoglobin. Your body drains its iron stores first and only then lets haemoglobin fall. During that window a CBC can look entirely normal while you feel exhausted.

Serum ferritin measures the stores themselves, which is why it is worth adding rather than relying on the blood count alone. This matters particularly for women with heavy periods, where slow loss over years empties the reserve gradually.

3. Thyroid

An underactive thyroid slows everything down — energy, digestion, heart rate, mood. It also produces weight gain, cold intolerance and hair fall, which is why it is so often confused with the two causes above.

A thyroid profile settles it. TSH alone is usually enough to screen; the full profile helps when TSH is borderline or the picture is confusing.

4. Vitamin D

Deficiency is very common in Pakistan, and not only in people who avoid the sun. Air quality, covered clothing, working indoors and darker skin all reduce how much vitamin D the skin produces. It presents as aching bones, muscle weakness, low mood and fatigue.

Vitamin D is straightforward to measure and straightforward to correct.

Why testing all four together makes sense

These four conditions overlap almost completely in how they feel. Someone can easily have two of them at once — iron deficiency and vitamin D deficiency together is a common combination — and treating one while missing the other produces the frustrating experience of taking supplements for months and feeling no better.

Our Women's Wellness and General Health Screening packages exist largely because of this pattern.

What blood tests will not explain

Be clear-eyed about the limits. Blood tests do not diagnose:

• Sleep debt or sleep apnoea, probably the single largest cause of daytime tiredness
• Depression and anxiety, which produce profound physical fatigue
• Chronic stress and overwork
• Medication side effects

If all four tests come back normal, that is genuinely useful information — it redirects the search rather than ending it.

If your tiredness came with unexplained weight loss, fever, night sweats or new breathlessness, do not wait to work through a testing sequence. See a doctor promptly.