Nutrient deficiencies are unusual among health problems in that they are common, cheap to test for, and straightforward to correct. They are also easy to misattribute — fatigue, thinning hair and poor concentration get filed under stress or age long before anyone orders a blood test.
Key takeaways
- Vitamin D, iron, vitamin B12, folate, magnesium and iodine are among the most common shortfalls in European adults.
- Symptoms overlap heavily, which is why self-diagnosis is unreliable.
- Blood tests are inexpensive and definitive for most of these. Test before supplementing.
- Some nutrients — iron in particular — are genuinely harmful in excess. More is not safer.
The six worth knowing about
Vitamin D
Widespread at northern latitudes, particularly through winter, and more common in people with darker skin, those who cover up, and those who spend little time outdoors. Presents as fatigue, muscle weakness, bone and joint aches, and low mood. Many national health bodies recommend a supplement during autumn and winter.
Iron
The most common nutritional deficiency worldwide, and most prevalent in menstruating women. Fatigue that rest does not fix, breathlessness on mild exertion, pale skin, brittle nails, hair shedding and sometimes a craving for ice. Diagnosed with ferritin and a full blood count.
Vitamin B12
Risk rises with age as stomach acid production falls, and with vegan diets, metformin use and long-term acid-suppressing medication. Symptoms include fatigue, pins and needles, memory and concentration problems and a sore tongue. Untreated B12 deficiency can cause lasting neurological damage, so this one is worth taking seriously.
Supplementing on a hunch treats the anxiety, not the deficiency. A blood test costs less than three months of guessing.On testing before treating
And three more
Folate
Overlaps with B12 — fatigue, mouth ulcers, irritability. Particularly important before and during pregnancy, where supplementation is standard advice.
Magnesium
Harder to assess, because blood levels are a poor reflection of body stores. Associated with muscle cramps, poor sleep and low mood. Dietary sources — nuts, seeds, legumes, leafy greens, wholegrains — are the sensible first move.
Iodine
Often overlooked. Intake has fallen in populations that have moved away from dairy and iodised salt toward plant milks, most of which are not fortified. Matters for thyroid function, and matters a great deal in pregnancy.
Test, then treat
The sensible sequence is unglamorous. Ask your GP for a blood panel covering vitamin D, ferritin and full blood count, B12 and folate, and thyroid function if fatigue is the main complaint. Take the results and correct what is actually low, at a dose someone has chosen deliberately.
A broad-spectrum multivitamin or a fortified meal replacement can reasonably cover general dietary gaps. Neither is a substitute for finding out that your ferritin is 8.
Do not self-prescribe iron. Iron overload causes organ damage, and the symptoms of too much overlap with the symptoms of too little. Iron supplements should follow a blood test, not precede one. The same caution applies to high-dose vitamin D and any supplement taken alongside prescription medication.
The pattern to watch for
One symptom is noise. Several together, persisting for more than a few weeks, is a signal — particularly if it includes fatigue that sleep does not resolve. That combination is worth a blood test rather than another month of assuming it is just a busy period.
Sources and further reading
- NIH Office of Dietary Supplements. Nutrient fact sheets for health professionals. ods.od.nih.gov/factsheets/
- NHS. Live Well: eat well, exercise and sleep guidance. www.nhs.uk/live-well/
- Mayo Clinic. Healthy lifestyle: nutrition and fitness. www.mayoclinic.org/healthy-lifestyle
- British Nutrition Foundation. Nutrition science and healthy eating resources. www.nutrition.org.uk/
This article is general information and is not a substitute for advice from a qualified clinician.
