Tired all the time? The blood tests that find fixable causes of fatigue

Feeling tired all the time is one of the most common reasons people see a doctor. Often the cause is life itself: too little sleep, stress, a new baby, long hours or low mood. But sometimes there is a physical cause that a simple blood test can find, and many of those causes are easy to fix once they are known.

A blood test will not explain every kind of tiredness. What it does well is rule in or rule out a short list of problems that are common, measurable and treatable. That is exactly what the Energy and Nutrients panel is built around.

Anaemia and the full blood count

Anaemia means your blood carries less oxygen than it should, because haemoglobin is low. The result is tiredness, breathlessness on stairs, a racing heart with effort and sometimes pale skin. LifePrint uses the WHO 2024 cut-offs: haemoglobin below 13.0 g/dL in men and below 12.0 g/dL in non-pregnant women is anaemia.

The size of the red cells, shown as MCV, gives a clue to the cause. Small cells point towards iron deficiency. Large cells point towards low B12 or folate, alcohol, thyroid problems or some medicines. The white cells and platelets in the same count help rule out other causes of tiredness, such as infection.

Iron stores

You can run low on iron long before your haemoglobin drops. Ferritin measures your stored iron, and a low ferritin can cause tiredness, poor concentration, hair shedding and reduced exercise tolerance even when the blood count is normal. Transferrin saturation shows how much iron is actually available to your body right now. Iron loss through periods, pregnancy, blood donation and a diet low in iron are the usual reasons, but in men and in women after menopause, low iron always needs a doctor to look for a cause.

Vitamin B12 and folate

Both vitamins are needed to make healthy red cells and to keep nerves working. Low levels can cause tiredness, low mood, poor memory and, with B12, pins and needles or unsteadiness. People on plant-based diets, people taking metformin or long-term acid-reducing medication, and older adults are most at risk of low B12. LifePrint tests active B12, the part your cells can actually use.

Vitamin D

Low vitamin D is common in South Africa, even with all our sunshine, especially in winter and in people who work indoors. Its main proven role is in bone and muscle health. The evidence that low vitamin D causes tiredness is weaker than for iron or B12, so a low result is worth correcting, but it may not be the whole answer.

Magnesium

Magnesium matters for muscles, nerves and heart rhythm. Low levels are uncommon in healthy people but more likely with some diuretics, long-term acid-reducing medication, heavy alcohol use or ongoing diarrhoea. Muscle cramps and weakness are more typical than tiredness alone.

The thyroid

An underactive thyroid slows the body down, causing tiredness, feeling cold, weight gain, dry skin and constipation. TSH is the best single screening test, and the Energy and Nutrients panel includes it. If your TSH is outside the range, the Thyroid panel adds free T4, free T3 and TPO antibodies to show what is going on. If you take biotin, pause it for 48 hours before your test, because it can distort thyroid results.

What the panel does not cover

Fatigue has many causes that this panel is not designed to find. Some are in the blood and covered by other LifePrint panels, others are not in the blood at all.

• Blood sugar, kidney and liver health, which are part of the Essentials panel.
• Sleep problems, including sleep apnoea, which often shows as loud snoring and daytime sleepiness.
• Depression and anxiety, which commonly present as tiredness first.
• Side effects of medication, such as some blood pressure tablets, antihistamines and antidepressants.
• Long recovery after a viral illness.

Reading your results

Your LifePrint report explains each result in plain language. Some results will sit in a grey zone, for example a ferritin between 15 and 30 ug/L, which is not deficiency but may still matter if you have symptoms. The report shows these separately and tells you how urgently to follow up on anything flagged.

If everything comes back normal, that is useful information too. It points you and your doctor towards the other causes of tiredness, and it saves you from taking supplements you do not need.

Whatever the results show, avoid starting iron, B12 or other supplements on your own before speaking to a registered healthcare practitioner. Taking them before the cause is known can hide the problem, and some, like iron, can do harm when they are not needed. Your report is health information, not a diagnosis.