Low energy is one of those symptoms that's easy to attribute to a busy life, but it's worth taking seriously. Vitamin D, vitamin B12 and iron deficiency are three of the most frequently identified — and correctable — causes of persistent fatigue in adults. They're also common enough in the North West that a GP will often check all three as a starting point.
Vitamin D deficiency
The UK doesn't get enough sun for most of the year, and Vitamin D is produced by the skin in response to sunlight. That makes deficiency genuinely common, particularly through autumn and winter — and particularly in the North West, where grey skies are more reliable than sunshine.
Low vitamin D is associated with:
- Persistent tiredness and low mood
- Muscle weakness or aches
- Reduced bone density over time
The NHS advises that most adults in the UK should consider a vitamin D supplement through winter months. But if your symptoms are significant, a blood test can confirm whether your levels are low enough to require more specific attention. It's worth knowing your actual level rather than guessing.
Vitamin B12 deficiency
B12 is essential for nerve function and the production of healthy red blood cells. Deficiency is more common than most people realise, particularly in:
- People following a vegan or strict vegetarian diet (B12 is found mainly in animal products)
- Older adults, whose ability to absorb B12 from food decreases with age
- People with certain gut conditions that affect absorption
Symptoms of B12 deficiency can include fatigue, brain fog, tingling in the hands or feet, and low mood. In more significant cases, it can affect memory and balance. A simple blood test measures your serum B12 level, and a GP can advise on the appropriate next steps — whether that's dietary changes, supplements, or something else entirely.
Iron deficiency
Iron is needed to make haemoglobin — the protein in red blood cells that carries oxygen around the body. When iron stores run low, your body's ability to transport oxygen is reduced, and tiredness is often the first sign.
Iron deficiency is particularly common in:
- Women of reproductive age due to monthly blood loss
- People with heavy periods
- Those with low dietary iron intake
A full blood count will detect anaemia, but iron deficiency can cause symptoms even before anaemia develops. A ferritin test (which measures stored iron) is a more sensitive early marker and is included in a proper iron screen.
Can I just take supplements without testing?
It's tempting to buy supplements and see if you feel better. The problem is that self-supplementing without knowing your levels means you might be addressing the wrong thing, or taking doses that aren't appropriate. Some supplements — particularly iron — can have side effects at higher doses, and too much vitamin D over time isn't harmless either. Starting with a blood test gives you an accurate baseline.
Getting tested in Preston
All three deficiencies are covered in our blood screens at Northwest Health — Silver (£200), Gold (£350) and Platinum (£500). No referral is needed, appointments are available quickly, and a GP reviews every set of results before you receive them.
Find out more about our blood tests →
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