The UK supplement market is worth over £500 million a year. Most of it is spent without testing. You might be taking vitamin D when your real problem is B12. Or supplementing iron when your ferritin is being masked by inflammation. Test first. Supplement what you actually need.
These are the nutritional markers most commonly deficient in the UK population and most impactful on how you feel day to day.
The most common deficiency in the UK. Between October and March, sunlight is insufficient for vitamin D synthesis at UK latitudes. Deficiency causes fatigue, low mood, muscle weakness, bone pain, and impaired immune function. The NHS reference range starts at 25 nmol/L but optimal is 75 to 125 nmol/L. A level of 35 is technically "normal" but far from where you want to be. Your TrueVitals report shows where you sit relative to optimal, not just the minimum, and recommends a specific daily dose based on your current level.
Essential for nerve function, red blood cell production, DNA synthesis, and energy metabolism. Deficiency causes fatigue, brain fog, tingling in hands and feet, mood changes, and cognitive decline. Common in vegetarians, vegans, people over 50 (reduced absorption), those on metformin or PPIs, and women on the contraceptive pill. TrueVitals recommends sublingual methylcobalamin for supplementation when levels are suboptimal, as it bypasses absorption issues in the gut.
Critical for DNA synthesis, cell division, and neural tube development in pregnancy. Serum folate reflects recent dietary intake and can fluctuate day to day. Red cell folate, available in the TrueVitals Ultimate panel, gives a more accurate 2 to 3 month average. The distinction matters because someone with normal serum folate can still have depleted long-term stores. Essential for anyone considering pregnancy.
The most common nutritional deficiency globally. Ferritin alone can be falsely elevated by inflammation, giving a false "normal." Full iron studies (ferritin, serum iron, TIBC, transferrin, transferrin saturation) give the true picture. A ferritin of 40 with a transferrin saturation of 12% is functionally deficient. Without the full panel, you would never know. Full iron testing guide →
Involved in over 300 enzymatic reactions. Deficiency causes muscle cramps, poor sleep, anxiety, fatigue, and irregular heartbeat. Difficult to assess accurately because only 1% of body magnesium is in the blood (the rest is in bones and soft tissue). Serum magnesium is an imperfect marker but it is the best routinely available measure, and low serum magnesium almost always indicates genuine deficiency. TrueVitals includes serum magnesium in every panel.
Essential for immune function, wound healing, testosterone production, and thyroid hormone synthesis. Deficiency is common in vegetarians, athletes (lost through sweat), and people with gut conditions. Symptoms include frequent infections, slow wound healing, hair loss, and impaired taste. TrueVitals includes zinc in the Signature panel (200+ biomarkers, £799).
Laboratory reference ranges define "normal" as the range that 95% of the population falls within. That includes people who are symptomatic, unwell, or suboptimal. Being within the reference range means you are not clinically deficient. It does not mean you are thriving.
Both are "within range." One is associated with fatigue, low mood, poor immune function, and increased fracture risk. The other is associated with optimal bone health, immune resilience, and reduced cardiovascular risk. The reference range does not distinguish between them. TrueVitals does.
Both are "normal." A B12 of 200 sits at the bottom of the reference range and is associated with neurological symptoms in many people. A B12 of 500 is solidly optimal. The difference matters enormously for energy, cognition, and nerve function.
Both are "in range." A ferritin of 15 means severely depleted iron stores with significant fatigue impact. A ferritin of 80 means healthy reserves. Most GP results sheets would flag neither as abnormal.
Both technically normal. The lower end is associated with muscle cramps, poor sleep, and increased anxiety. The upper end indicates adequate stores. The difference is whether you supplement or not.
Every TrueVitals report shows your results against both the laboratory reference range and the optimal range. Suboptimal results are flagged with specific supplementation recommendations including form, dose, and timing.
The average UK adult takes 2 to 3 supplements daily. Most have never tested their levels. Here is why that is a problem.
Taking vitamin D year-round when your levels are already optimal is unnecessary and a waste of money. Testing tells you what you actually need and what you can stop taking.
Fatigue? You assume iron and take a supplement. But your iron is fine and your B12 is depleted, or your thyroid is suboptimal, or your vitamin D is low. Without testing, you treat the wrong deficiency.
Iron overload causes organ damage. Excessive vitamin D causes hypercalcaemia. High-dose B6 causes nerve damage. Zinc excess depletes copper. Testing ensures you stay in the therapeutic range and avoid harm.
A vitamin D level of 30 nmol/L needs a different dose than a level of 60. Your TrueVitals report calculates specific doses based on your current level, body weight, and target range, rather than a generic "one tablet daily."
Low B12 despite supplementation could mean an absorption issue (intrinsic factor, parietal cell problems, gut dysfunction). Low iron despite supplementation could mean inflammation is sequestering it. Testing reveals whether your supplements are actually working.
Iron blocks zinc absorption. Calcium blocks iron absorption. Magnesium competes with calcium. Vitamin D requires adequate magnesium to be activated. A comprehensive panel identifies all the relevant levels so supplementation can be coordinated properly.
Your report does not just tell you what is low. It tells you exactly what to take, in what form, at what dose, and when.
Not all supplement forms are equal. We recommend methylcobalamin (not cyanocobalamin) for B12 because it is bioactive. Iron bisglycinate (not ferrous sulphate) for iron because it is better tolerated. Vitamin D3 with K2 for optimal calcium metabolism. Magnesium glycinate or threonate depending on whether sleep or cognitive function is the priority.
Your dose is calculated based on your current level, your target level, your body weight, and the bioavailability of the recommended form. "Take 2,000 IU of vitamin D" is generic. "Take 4,000 IU of vitamin D3 with K2 for 3 months, then retest to confirm you have reached 75 to 100 nmol/L" is personalised.
Iron on an empty stomach, away from calcium and zinc. Vitamin D with a fat-containing meal for absorption. Magnesium in the evening for sleep benefit. B12 sublingual in the morning. Timing affects absorption and efficacy. Your report includes this for every recommendation.
Different nutrients take different amounts of time to respond. Iron stores take 3 months to rebuild. Vitamin D takes 6 to 8 weeks to reach steady state. B12 responds within weeks if absorption is intact. Your report tells you when to retest to confirm the intervention is working.
Vitamin D, B12, serum folate, red cell folate, full iron studies (not just ferritin), magnesium, zinc, and calcium. TrueVitals includes all of these in every panel from Advanced (£269). The Ultimate panel adds red cell folate for a more accurate long-term folate assessment.
The NHS tests vitamin D, B12, and folate if a GP suspects deficiency. Magnesium, zinc, and full iron studies are rarely tested routinely. A private comprehensive blood test covers all nutritional markers alongside the systems they affect (thyroid, inflammation, hormones, blood count).
For the most accurate picture of your baseline status, stop supplements containing the nutrients being tested for 3 to 5 days before your blood draw. If you want to check whether your current supplements are working, keep taking them as normal and your results will reflect your supplemented state. Either approach is useful for different reasons. Note this in your lifestyle quiz.
TrueVitals Advanced (74 markers, £269) covers vitamin D, B12, folate, full iron studies, magnesium, zinc, and calcium alongside thyroid, hormones, and inflammation for full context. The Ultimate panel (114, £349) adds red cell folate. No other UK provider tests this many nutritional markers alongside the systems they influence. Compare all panels.
Yes. Vitamin D deficiency is driven by UK latitude and sunlight, not diet. B12 absorption declines with age regardless of intake. Iron status depends on menstrual losses, inflammation, and absorption, not just dietary iron. Magnesium depletion from soil has reduced levels in food over decades. A healthy diet reduces risk but does not guarantee sufficiency.
Vitamin D, B12, folate, full iron studies, magnesium, zinc, and calcium. Plus the systems that affect them. Personalised supplement recommendations. From £269.
.png)