Which Vitamin and Mineral Deficiencies Cause Fatigue?

Feeling constantly tired is one of the most common reasons people seek a health check — and nutrient deficiencies are among the most treatable causes. Several vitamins and minerals play a direct role in how your body produces energy, so when any of them run low, fatigue often follows. Here are the usual culprits, what each one does, and why it makes sense to check them together.

The common nutrient culprits

Vitamin D

Made mostly from sunlight, vitamin D is widely lacking in the UK, especially in winter. Low levels are linked to tiredness, aching muscles and low mood — and because it's so common, it's one of the first things worth checking.

Vitamin B12 (active B12)

B12 keeps nerves and red blood cells healthy and helps release energy from food. Deficiency can cause fatigue, tingling, brain fog and breathlessness. An active B12 measurement can pick up a shortfall that a standard B12 test might miss.

Folate

Folate (vitamin B9) works hand in hand with B12 to make healthy red blood cells. When it's low, you can develop a type of anaemia that leaves you drained and short of breath.

Ferritin (iron stores)

Iron is needed to carry oxygen around the body. Low ferritin — your iron reserve — is a leading cause of fatigue, particularly in women with heavy periods, and often appears before full-blown anaemia does.

Magnesium

Magnesium is involved in hundreds of energy-related reactions and in muscle and nerve function. Low levels can contribute to tiredness, muscle cramps and poor sleep.

Zinc

Zinc supports immunity, wound healing and metabolism. A shortfall can leave you feeling run down and more prone to infections, which in turn saps energy.

Why a combined screen beats one-at-a-time testing

Because tiredness rarely points to a single nutrient, testing markers individually often means repeat blood draws and weeks of waiting when the first result comes back normal. A combined vitamin and mineral screen measures the common culprits — vitamin D, active B12, folate, ferritin, magnesium and zinc — from one sample, so you and your doctor get the full picture in one go.

Fatigue isn't always about nutrients

It's worth remembering that tiredness has many non-nutritional causes too — an underactive thyroid, poor sleep, stress and low mood among them. That's why normal deficiency results are still genuinely useful: they rule out the common nutrient causes and help point you and your doctor towards what else might be going on.

When to get checked

If you've been tired for more than a few weeks despite reasonable sleep, a deficiency screen is a sensible, efficient first step. It replaces guesswork with clear numbers you can act on.

Written by Dr Ibrar Ahmed — MBChB MRCP MRCGP PhD PG Dip (Cardiology)
Specialist interest: Cardiovascular Medicine · OneMedicine, CQC-registered clinic