Anatomy
Nutrition affects every organ and tissue in the body, from bone marrow and muscles to the brain, immune system and skin.
Organ Health · Vitamins & Nutrition
Vitamins & Nutrition
Understand how key vitamins and minerals support energy, immunity, blood cell production and bone health, and how laboratory tests reveal deficiencies.
Educational information only. Detectives Health helps explain laboratory tests and organ health in plain English. It does not diagnose disease, prescribe treatment or replace professional medical advice. Please discuss your individual results with a qualified healthcare professional.
Understanding the organ
Anatomy, function and importance
Function
Vitamins and minerals act as cofactors that enable thousands of biochemical reactions, from producing red blood cells to maintaining nerves.
Why it matters
Balanced nutrition supports energy, immunity, cognition, growth, mood and long-term wellbeing.
How it works
A simple explanation in plain English
Nutrients are absorbed from food in the gut and transported around the body in the blood.
Some, such as iron and vitamin B12, are essential for making healthy red blood cells.
Others, such as calcium and vitamin D, are needed for bones and muscles, while zinc and vitamin C support immunity.
Deficiencies often develop slowly and may not cause symptoms until levels are quite low.
Laboratory tests
Which laboratory tests assess this organ
Each test contributes a small piece of information. Results are always interpreted alongside symptoms, medical history and other investigations.
Ferritin
- What it measures
- The body's stored form of iron.
- Why it is requested
- One of the most sensitive tests for iron deficiency.
Iron
- What it measures
- The amount of iron circulating in the blood.
- Why it is requested
- Interpreted alongside ferritin and transferrin saturation.
Vitamin B12
- What it measures
- A vitamin essential for red blood cells and nerve health.
- Why it is requested
- Reviewed in anaemia, fatigue and neurological assessments.
Folate
- What it measures
- A B vitamin essential for cell division and red cell production.
- Why it is requested
- Often reviewed alongside B12.
Vitamin D
- What it measures
- A vitamin important for calcium absorption and bone health.
- Why it is requested
- Reviewed in bone, muscle and immune assessments.
Zinc
- What it measures
- A mineral needed for immunity, wound healing and taste.
- Why it is requested
- Reviewed when deficiency is suspected.
Magnesium
- What it measures
- A mineral supporting muscles, nerves and enzyme activity.
- Why it is requested
- Reviewed in cramps, palpitations or specific medical conditions.
Copper
- What it measures
- A mineral involved in iron metabolism and connective tissue.
- Why it is requested
- Reviewed in specialist contexts.
Selenium
- What it measures
- A mineral supporting antioxidant defences and thyroid function.
- Why it is requested
- Reviewed in specialist contexts.
Factors that influence results
Why results vary between people and over time
Laboratory values are shaped by many day-to-day factors. Understanding them helps you and your healthcare professional interpret results in context.
Diet
Restrictive diets, ultra-processed foods and low variety may increase deficiency risk.
Age
Absorption of some nutrients such as B12 declines with age.
Gut health
Conditions such as coeliac disease and inflammatory bowel disease affect absorption.
Pregnancy
Pregnancy increases the need for many nutrients including folate, iron and vitamin D.
Medication
Certain medications may reduce absorption of specific nutrients.
Menstruation
Regular menstrual blood loss increases iron requirements.
Alcohol
Regular high intake affects the absorption of several B vitamins.
Sun exposure
Vitamin D depends significantly on sensible sun exposure.
Preparing for your blood test
Practical educational guidance
Preparation varies between laboratory tests. Always follow the specific instructions from the clinician or laboratory that requested your sample.
- Follow any fasting instructions given by the requesting clinician — some tests such as fasting glucose or a lipid profile need 8–12 hours without food.
- Take regular medication as usual unless your healthcare professional advises otherwise.
- Mention any supplements — biotin, high-dose vitamins and herbal remedies can influence several laboratory tests.
- Stay well hydrated with water in the hours before your test; dehydration can affect several markers.
- Avoid unusually strenuous exercise in the 24 hours before testing, as this may temporarily alter some results.
- Where possible, attend at a consistent time of day — several hormones and enzymes follow daily rhythms.
- Postpone routine testing if you have an acute infection, unless your clinician specifically wants a result during illness.
Healthy lifestyle
Everyday habits that support this organ
Consistent healthy habits may support organ function over time. They do not replace medical assessment when concerns arise.
Eat a rainbow
A wide variety of vegetables and fruits provides different vitamins and antioxidants.
Include quality protein
Lean meat, fish, eggs, legumes and dairy support iron, zinc and B12 intake.
Whole grains
Whole grains provide B vitamins, magnesium and fibre.
Oily fish or plant sources
Oily fish, walnuts, flaxseeds and rapeseed oil support essential fatty acid intake.
Consider vitamin D
A daily vitamin D supplement is widely recommended in the UK in autumn and winter.
Discuss supplements
Discuss supplements before starting them, especially in high doses.
Moderate alcohol
Following low-risk drinking guidance protects B vitamin balance and the liver.
Regular meal patterns
Regular meals help stable energy and nutrient intake.
Symptoms to discuss
Changes worth mentioning to a healthcare professional
These symptoms do not confirm any diagnosis. They are educational prompts for a professional assessment when they are new, persistent or worsening.
- • Persistent tiredness
- • Pale skin
- • Breathlessness on mild exertion
- • Restless legs
- • Sore tongue or mouth
- • Tingling or numbness
- • Brittle nails or hair changes
- • Frequent minor infections
Routine monitoring
Health checks and screening in an educational context
Recommendations vary between individuals. Your healthcare professional will advise which tests apply to you and how often.
- Include full blood count and ferritin in relevant health reviews
- Discuss vitamin B12 and folate testing if symptoms suggest
- Consider vitamin D testing in bone or muscle concerns
- Discuss individual supplement needs with your GP or pharmacist
- Follow personalised monitoring plans in gut or absorption conditions
- Discuss dietary patterns openly at annual reviews
Questions you may wish to discuss
Prompts for your next healthcare appointment
These are educational conversation starters — not a script. Bring the ones that feel most relevant to your situation.
- What does this result mean in my individual situation?
- Should the test be repeated, and if so when?
- Are further investigations recommended based on this result?
- Could any of my medications or supplements be influencing the result?
- Are lifestyle changes likely to help, and which ones would you prioritise?
- How does this result fit with my symptoms and medical history?
- What would prompt a change of plan or a specialist referral?
Frequently asked questions
Common educational questions
Q.Do I need to take supplements?
Many people can meet nutritional needs from a varied diet, but some benefit from specific supplements such as vitamin D. Individual advice depends on diet, life stage and medical history.
Q.Is iron deficiency common?
Iron deficiency is common, particularly in women of reproductive age. It should always be investigated to understand the underlying cause.
Q.Can I take too many vitamins?
Yes. High doses of some vitamins and minerals may cause harm. Follow product guidance and discuss with a healthcare professional.
Q.How is vitamin D deficiency corrected?
It is usually corrected with a course of vitamin D followed by a maintenance dose, alongside dietary and lifestyle measures.
Biomedical Scientist's insight
The science behind your result
Biomedical Scientists perform, validate and quality-check laboratory analyses before results are authorised for release. Every test is run against calibrated standards and internal controls, and reviewed for analytical accuracy. Laboratory findings are then interpreted by healthcare professionals alongside your symptoms, examination findings and medical history — which is why context matters as much as the number on the report.
Continue learning
Related Detectives Health modules
Scientific leadership
Steve Diongo
Founder & Scientific Lead · HCPC-Registered Specialist Biomedical Scientist · 15+ years NHS · 20+ years laboratory medicine
This module has been developed and reviewed by the Detectives Health Professional Team under the scientific leadership of Steve Diongo. Educational content is regularly updated using recognised laboratory standards, current scientific evidence and professional best practice.
Reviewed against NHS, NICE, CDC, WHO and USPSTF guidance.
Educational information only. Detectives Health does not diagnose disease, prescribe treatment or replace professional medical advice.
Please discuss your individual laboratory results, symptoms and health concerns with a qualified healthcare professional.