Vitamin deficiency symptoms: how to recognise them?

Persistent fatigue, brittle nails, fragile immunity: 10 warning signals to recognise. But also: why only a blood test settles it.

No single symptom diagnoses a deficiency on its own. But the accumulation of subtle signals over several weeks should alert you and prompt a biological check.

The main deficiency signals are persistent fatigue (iron - B12, vitamin D), hair loss and brittle nails (iron, zinc, biotin), fragile immunity (vitamin C - D, zinc), night cramps (magnesium) and low mood (B12, folate, vitamin D). All are non-specific: only a blood test truly settles it.

10 signals to know

• Persistent fatigue not explained by sleep or stress (think: iron - B12, vitamin D).
• Hair loss or dull hair (biotin, iron, zinc, vitamin D).
• Brittle nails, vertical ridges (biotin, iron, zinc).
• Fragile immunity, repeated colds (vitamin C, vitamin D, zinc).
• Night cramps (magnesium, potassium).
• Bleeding gums (vitamin C, vitamin K).
• Dry skin, seborrhoeic dermatitis (vitamin B2 - B6, vitamin A, omega-3).
• Easy bruising (vitamin C, vitamin K).
• Low mood, subtle cognitive trouble (B12, folate, vitamin D, omega-3).
• Susceptibility to urinary infections or recurrent candidiasis (zinc, vitamin D, iron).

Why only a blood test settles it

All these symptoms are non-specific: they may reflect a deficiency, an inflammatory syndrome, a thyroid disorder, a hormonal imbalance or simply poor lifestyle. The biological panel (CBC, ferritin, 25(OH) vitamin D, B12, folate, erythrocyte magnesium) brings you back to measurement.

What to do

Note your symptoms for 4 weeks (a simple journal). If they persist, see your doctor for a panel. In the meantime, a 100% NRV multivitamin won't hurt and can fill the most likely gaps.

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