Your Blood Test Results Explained

Written by the Fix My Hair Editorial Team · Clinician-reviewed by Dr Hisham Band · GMC No. 7550130 · Last reviewed 27 Feb 2026

Medical reference ranges are designed for general health — not specifically for hair health. Your results might be “normal” by standard measures and still be affecting your hair.

Optimal vs “normal”

The level needed for healthy hair is often higher than the standard reference range — ferritin is the clearest example. “Normal” and “optimal for hair” are not the same thing.

What each marker tells us

Vitamin D plays a direct role in follicle cycling, DHT indicates how aggressive the condition is, and thyroid markers affect hair in their own distinct way.

How we read it

Every patient receives a plain-language interpretation — not just a printout of numbers.

“Normal” versus “optimal”

The most important idea when reading a hair-loss panel is that the lab’s “normal range” isn’t the same as the level that’s best for your hair. Reference ranges are built to flag disease across the whole population; hair follicles are demanding, and a value at the low end of normal can still limit growth. We read your results against optimal targets for hair, not just “not deficient.”

Ferritin

Your iron store, and one of the most relevant numbers for hair. Anaemia is flagged only at low haemoglobin, but hair can suffer with low ferritin long before that — many clinicians look for a level comfortably above the bottom of the range (often cited around 50–70 ng/mL or higher) for healthy hair, rather than merely “not anaemic.” More in low ferritin and hair loss.

Thyroid (TSH, T3, T4)

Thyroid hormones regulate the hair cycle, and both under- and over-active thyroid cause diffuse shedding. A TSH at the edge of range, alongside symptoms, can be enough to affect hair — which is why we look at the full thyroid picture rather than a single number in isolation.

Vitamin D and B12

Low vitamin D is associated with hair loss and is extremely common in the UK; low B12 (more likely on plant-based diets) can also drive shedding. Both are simple to correct, and both are frequently “low-normal” rather than overtly deficient — another place the standard range can mislead.

Zinc and other markers

Zinc deficiency is a recognised cause of hair loss, and depending on your picture we may look at inflammatory or other markers too. The point isn’t to chase every number, but to read the whole panel together — deficiencies often cluster, and one low marker prompts a closer look at the rest.

Hormonal markers

Testosterone, DHT and related hormones help confirm whether androgenetic (pattern) loss is in play, and in women can point to conditions like PCOS that need their own management. These results shape whether DHT-lowering treatment is appropriate.

What we do with your results

Reading the numbers is only half the job; the value is in the plan that follows. Your results translate into specifics: correct this deficiency, start that treatment, monitor this marker, or — reassuringly — everything’s optimal and your loss is purely genetic, so here’s the plan for that. You leave understanding not just what your numbers are, but what they mean for your hair.

Common questions

My GP said my results were normal — why read them differently? Because we look for optimal-for-hair levels, not just the absence of disease. “Normal” and “optimal” aren’t the same thing.

How soon do results come back? Typically a few working days, after which we go through them with you.

Why We Test Before We Treat

Low Ferritin and Hair Loss

The Blood Test Your GP Never Ordered