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Top 10 Supplements to Test Before Use
Vitamin D
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9 min read

Top 10 Supplements to Test Before Use

What’s well-intended can quickly become too much of a good thing with some micronutrients – here, the rule is: better safe than sorry!The body is a complex system. And like any system, it has thresholds, feedback loops, and bottlenecks. Micronutrients in particular don’t act in a linear fashion: too little makes you sick – but so does too much.Many experts and influencers are now talking about micronutrient deficiencies and what you can do about them – and that’s a good thing, because deficiencies are likely more widespread and have greater (especially long-term) impacts on health and longevity than most doctors learned during their training. Then every so often, horror stories about overdoses pop up – especially involving vitamin D3.So what should you do?Generally, the principle “test first, then take” is a safe approach – as long as you know how to interpret your lab values and derive the right supplement strategy (or dietary optimization) for you. But that’s a topic for another article.Fortunately, there are micronutrients where deficiency is not unlikely, where supplementation is often beneficial, and where dangerous overdosing is hardly possible with standard doses: Top 10 supplements you can safely take without a lab test! (Note: In a future update of this article, omega 3 – and possibly astaxanthin – will likely be added to the Top 10. Thanks for the great discussion on LinkedIn!)But let’s get to today’s topic: for some micronutrients, the risk of overdose is higher, and lab testing becomes more important – specifically, we’re talking about:Fat-soluble vitamins (which are stored in the body) andtrace elements with a narrow therapeutic range.Here are 10 substances you should definitely not supplement without checking your blood values first.Note on the target values listed for each nutrient: These roughly reflect the consensus range found in publications by the following German-speaking experts: Dr. Helena Orfanos-Boeckel, Dr. Thiemo Osterhaus, Dr. Ulrich Strunz, Dr. Uwe Gröber, and Dr. Volker Schmiedel.Vitamin A (Retinol) – A tricky caseWhat is it good for?Vitamin A is essential for healthy skin, mucous membranes, vision, blood vessels, and a strong immune system. Its active form, retinol, is particularly important for regulating genes that control cell growth and differentiation.A deficiency can manifest as dry eyes, light sensitivity, increased susceptibility to infections, or delayed wound healing.When articles are published in autumn/winter about immune-boosting micronutrients, vitamin A – like amino acids – is rarely mentioned. So if you’ve already optimized your vitamin D, vitamin C, zinc, and selenium levels but still catch every virus going around, it may be time to check your vitamin A status.Special note: The body can convert beta-carotene (e.g., from carrots) into retinol – but this conversion is genetically impaired in up to 45% of the population (especially due to BCMO1 polymorphisms). In such cases, beta-carotene won’t help much.Too much is too much?Oh yes. Retinol is stored in the liver – too much over time can lead to toxic effects. Liver issues, headaches, hair loss, and bone weakening are just some possible consequences. Especially problematic is an overdose during pregnancy – it can lead to severe birth defects.So extra caution is required in cases of liver disease and during pregnancy!What could I do?If you supplement vitamin A, you should first check your fasting retinol level in the blood – possibly also with a genetic test for beta-carotene conversion. A potential target serum level is 600 to 700 µg/l.For long-term high-dose supplementation (up to 3,000 µg or 10,000 IU/day from all sources is considered safe by EFSA), it’s wise to monitor your liver enzymes (especially ALT/GPT) and watch for symptoms like fatigue, pressure in the upper right abdomen, or skin changes.Vitamin D (25-OH-D3) – Blessing and risk in oneWhat is it good for?Vitamin D is one of the most commonly supplemented vitamins – and for good reason. It regulates calcium levels, strengthens bones, supports the immune system, enhances muscle function, influences gene expression, and even impacts mood.Without adequate sunlight, especially in winter, levels drop quickly.A deficiency can manifest in many ways: muscle weakness, depression, osteoporosis, or susceptibility to infections.The Robert Koch Institute last assessed vitamin D levels in Germany from 2008 to 2011 and found that only 44% of adults had a serum concentration of at least 20 ng/ml – the minimum considered sufficient for bone health.The German Cancer Research Center notes that "taking vitamin D daily could reduce cancer mortality in the population by twelve percent."Too much is too much?Absolutely – vitamin D is a fat-soluble prohormone that, in excess (above 10,000 IU/day), can dangerously raise calcium levels. Consequences include kidney stones, fatigue, muscle weakness – or, in severe cases, cardiac arrhythmias.A particular trap is that the active forms are hormonally regulated, and the commonly measured 25-OH-D doesn’t always show the full picture.What could I do?Measuring 25-OH-D in your blood is the foundation – the target serum range is 40 to 60 ng/ml.Once you know your baseline, you can use an online calculator to determine your personal vitamin D requirement: typically, you’ll get a value for a one-time loading dose (to reach your goal) and a value for ongoing maintenance dosing.Note: EFSA considers up to 4,000 IU/day (or 100 µg) of vitamin D3 in total to be safe long-term.Most calculators only use body weight as a variable. But since vitamin D needs also depend on genetics and lifestyle (especially sun exposure), treat the result with caution and recheck your blood after an initial loading phase or after three months of supplementation.If levels remain low or seem off despite supplementation, check parathyroid hormone (PTH) – a high value may indicate a functional vitamin D deficiency. Some experts also recommend testing the active form 1,25-OH.For high-dose, long-term supplementation of vitamin D, you should also take at least 100–200 µg of vitamin K2 (as MK-7, all-trans) – many D3 supplements already include K2.Calcium and magnesium levels should also be considered.Vitamin E – Underestimated, but not harmlessWhat is it good for?Vitamin E is a powerful antioxidant that protects our cell membranes from oxidative stress. It also supports the immune system, helps maintain blood vessel health, protects nerves, and reduces inflammation.Deficiencies are rare but can occur with fat malabsorption disorders or certain genetic predispositions, and symptoms can vary: dry eyes, muscle weakness, light sensitivity, increased infection risk, or delayed wound healing.Too much is too much?Years ago, vitamin E was widely used in Germany, often in high doses as a preventive measure. The problem: daily doses over 1,000 mg can inhibit blood clotting. Anyone taking blood thinners or with a clotting disorder is at risk of internal bleeding.Excessive vitamin E can also interfere with vitamin K metabolism.Note: EFSA considers up to 300 mg (or 447 IU) per day in total to be safe long-term.What should I do? A target serum level for alpha-tocopherol is around 20 mg/l or 46 µmol/l. Testing should be done fasting to avoid distortion from dietary fats.If supplementing long-term at high doses, monitor vitamin K status (e.g., via ucOsteocalcin).Hint: Always take vitamin C too – it can recycle oxidized vitamin E!Side note: Alpha-tocopherol is only one of eight forms of vitamin E.Iron – Energiser or silent danger?What is it good for?Without iron, there’s no oxygen transport – that’s a given. Iron is used in hemoglobin and many enzymes and is crucial for mitochondrial energy production, cognitive performance (via neurotransmitters), and immune function.Iron deficiency is common – especially, but not only, in women with menstruation. Typical symptoms include fatigue, paleness, concentration problems, susceptibility to infections, and hair loss.Too much is too much?Definitely. Iron is also a powerful oxidant. Too much leads to free radical formation, damaging cells – especially in the liver, heart, and joints. Symptoms often appear only after years, which is why regular lab checks are so important!Especially dangerous: genetic iron metabolism disorders like hemochromatosis (C282Y, H63D).EFSA considers up to 40 mg of total daily iron intake to be safe long-term.What should I do?Supplementing iron can be tricky, as many people don’t tolerate common iron supplements well – it’s worth trying different forms (like orotate or bisglycinate) and timing (ideally on an empty stomach with some vitamin C, and away from other minerals).At minimum, ferritin (iron stores) should be tested – a target serum level is about 100–150 µg/l for women and around 200 µg/l for men.Also important for interpretation: transferrin saturation (target ~35%) and CRP, since ferritin can rise in inflammation even if iron is low.Zinc – Immune turbo with side effectsWhat is it good for?Zinc is involved in over 300 enzymatic reactions – including wound healing, insulin metabolism, DNA replication and transcription, antioxidant defense, immune function, hormone production (e.g., testosterone), and cell division.According to experts like Dr. Orfanos-Boeckel, zinc deficiency is not rare. The immune system suffers, skin becomes more vulnerable, wounds heal more slowly, taste perception decreases, and libido drops.Too much is too much?Absolutely. Too much zinc can cause nausea, dizziness, headaches, stomach upset, vomiting, and loss of appetite.Long-term high-dose zinc intake can reduce magnesium absorption and lead to copper deficiency. Zinc blocks copper absorption in the gut – which can, over time, cause anemia, disturbed fat metabolism (low HDL cholesterol), nerve damage, and increased susceptibility to infections.EFSA considers up to 25 mg of zinc per day in total to be safe long-term.What could I do?The best way to assess zinc status is with a full blood test – it’s more stable than serum levels. A target value is around 6 to 7 mg/l.If supplementing zinc, you should always keep an eye on your copper levels – (spoiler: copper will be covered in Part 2 of this article).Another hint for supplementation: Chris Masterjohn recommends splitting larger zinc doses – no more than 15 mg at a time.Interim summary: test before and test again laterWith all these micronutrients, the rule is: what’s meant to help can also harm – especially if dosed incorrectly!Fat-soluble vitamins and trace elements accumulate in the body. Symptoms of excess develop slowly and are often vague. That means toxicity often goes unnoticed – and becomes a real danger.In Part 2 of this article, we’ll take a closer look at copper, selenium, iodine, manganese, as well as calcium and potassium. Because the rule also applies to those: Test, don’t guess. Your metabolism is unique and complex. Then supplement intentionally – and test again to learn! 

Top 10 supplements you can safely take without a lab test
Antioxidants
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11 min read

Top 10 supplements you can safely take without a lab test

They do exist! These 10 supplements can usually be taken without any problems – no need for blood tests or other diagnostics.You already understand that it generally makes sense to first check whether you actually have a deficiency before taking a supplement. The “watering can” principle ("I’ll just take whatever my favorite health influencers recommend") may be easy to follow but can go wrong. Because with some micronutrients (and other supplements), too much can do real harm. This mainly applies to fat-soluble vitamins and trace elements. More on that in one of the upcoming articles.Today’s focus is on the exceptions to the “test first, then take” rule: Not every vital nutrient needs to be tested in the blood beforehand. For some, the benefits are clear even without numbers, the risks are manageable, and deficiency is not unlikely. But don't get me wrong: I don't say everybody has to supplement these compounds – it's a very individual decision and this article hopefully helps you a bit.And: "just take it" doesn't mean "pour it in blindly". That’s why you’ll find here a nuanced list of ten micronutrients that you can usually start with even without lab results – sometimes with a note on when it might still make sense to take a closer look.1. Magnesium – the underestimated all-rounderWhy should I consider to supplement?Magnesium is involved in over 300 enzymatic reactions – from muscle relaxation and energy production to stress regulation. The need increases with sports, stress, caffeine, or medication use (e.g. proton pump inhibitors).Experts assume a widespread deficiency.The different forms of magnesium are worth their own article, but with citrate, malate, and bisglycinate, you're very likely making a good choice. The NRV (Nutrient Reference Value – the amount a healthy person should consume daily to prevent deficiency symptoms) for magnesium is 375 mg.Two notes: To get 375 mg of elemental magnesium, you often need more than 3 grams of the compound depending on the form. And if you exercise or are under stress, your need is probably much higher.Either way: A supplement with 300 mg per day won’t hurt you.What happens in case of overdose?That’s the practical part: too much magnesium usually leads "only" to acute diarrhea – if so, try to switch to Bisglycinate (also see Glycine, below), Malate or Taurate (also see Taurine, below).And if I want to test anyway?Labs often measure serum values, but these are not very meaningful since most magnesium is stored inside cells. If you want to know more precisely, invest in a whole blood mineral analysis.2. Vitamin C – the water-soluble classicWhy should I consider to supplement?Vitamin C is essential for immune function, skin, connective tissue, and as an antioxidant. The need increases with physical stress, infections, injuries, inflammations – practically all the time.For few micronutrients are the recommended amounts so widely debated: The NRV is 80 mg daily, while Linus Pauling took up to 18 g daily in old age – spread throughout the day. A daily supplementation of 200 mg up to 500 mg is probably quite reasonable; during acute infections or after injury/surgery, possibly even more.Important: Do not take together with selenium!Otherwise, the form doesn’t matter much. “Ester-C” (a buffered form) is often recommended, as it’s apparently better tolerated by sensitive stomachs and seems to keep blood levels elevated longer.What happens in case of overdose?High doses (several grams per day) can cause diarrhea and, in sensitive individuals or people with a history of kidney disease, kidney stones.And if I want to test anyway?Since the separated plasma must be immediately frozen and protected from light, it’s best to have the blood sample taken directly at the lab.3. NAC (N-Acetylcysteine) – cell protection and mucus dissolverWhy should I consider to supplement?NAC boosts the body’s own production of glutathione – one of the most important antioxidants in the body. Especially helpful in cases of oxidative stress, environmental pollution, or (chronic) inflammation.NAC also acts directly on the lungs, as a classic mucus dissolver and as protection against fine dust and other air pollutants. More.Usual dosage: 600 mg, once, twice or thrice daily.What happens in case of overdose?Very high doses (more than 2–3 g) may cause nausea, vomiting, or diarrhea.If you have asthma, histamine or sulfur intolerance, you should be cautious. Do not take during pregnancy or breastfeeding.And if I want to test anyway?Cysteine is measurable in the blood but rarely tested, even in labs that offer amino acid profiles. Glutathione can be measured as a target structure, but it is relatively expensive.4. Glycine or Collagen – for joints, sleep, and structureWhy should I consider to supplement?Glycine is the most common amino acid in connective tissue and has a calming effect on the nervous system. With glycine or in combination with collagen peptides, you support skin, joints, regeneration, and sleep.You can use glycine as a mild sweetener and enjoy 3-5 grams or up to 10 grams per day or even more if you follow the protocol of Siim Land.What happens in case of overdose?Very high doses (over 15 g/day) can cause stomach discomfort, abdominal pain and nausea.And if I want to test anyway?Labs that offer blood tests for amino acids usually include glycine. However, it seems to be rare for glycine deficiency to occur in isolation.5. MAP (Master Amino Pattern) – efficient protein sourceWhy should I consider to supplement?MAP (also called EAA – Essential Amino Acids) provides the eight essential amino acids in the optimal ratio – almost completely bioavailable. Ideal for sports, aging, regeneration, or low-protein diets.With MAP, nearly all the contained protein is actually utilized by the body – about two to three times more efficiently than conventional whey protein – source: manufacturer information and studies by Lucà-Moretti. Common intake: 5 to 10 grams daily – or calculate your daily protein need, subtract your dietary protein, and take about the half of the gap as MAP.One hint: If you try a MAP/EAA powder, you should be aware that especially the amino acid L-Methionine does not taste too well if it gets in contact with water – I prefer to take capsules or tablets.What happens in case of overdose?The amino acids are either fully utilized or excreted. Virtually risk-free – except maybe for your wallet.And if I want to test anyway?Amino acid profiles are available in many labs, but relatively expensive. For a first look, the standard lab value “total protein” is a good start.6. Vitamin B-Complex – the underrated energy sourceWhy should I consider to supplement?B vitamins are crucial for energy, nerves, detoxification, and mental performance. Particularly useful during stress, physical activity, alcohol consumption, medication use, vegan diets, chronic inflammation, or pregnancy. Many experts report widespread deficiencies.It’s important to choose products with bioactive forms (e.g. P5P for vitamin B6). Even high-dose B-complex supplements are usually still within a safe range.What happens in case of overdose?B vitamins are water-soluble and excess amounts are excreted.Exception: B6 – consistently high doses can lead to nerve damage. So when in doubt, go for a product with a “not too high” dose (up to 25 mg) of vitamin B6.One note: if you observe your urine to become shiny yellow, sometimes appearing almost fluorescent, it’s usually a harmless sign of excess Vitamin B2, being excreted through the kidneys. You don’t like yellow? Ever thought about taking beetroot or Methylene Blue? ;)And if I want to test anyway?If you want to check your vitamin B levels, make sure the lab measures the bioactive forms.7. Choline – Brain Nutrient with Liver FunctionWhy should I consider to supplement?Choline is a precursor of acetylcholine (a neurotransmitter responsible for attention, concentration, and learning), supports the liver, and is essential for cell membranes. Particularly relevant for vegan diets, pregnancy, or high mental demands.Chris Masterjohn states that a Choline deficiency might be one cause of the “non alcoholic fatty liver” pandemic.Once again, it depends on the form: Avoid Choline Bitartrate – it’s cheap but poorly bioavailable and leads to high TMA/TMAO levels. Recommended are phosphatidylcholine (e.g., in lecithin), Alpha-GPC, and CDP Choline (Citicoline), with the latter two having a stronger effect on neurotransmitters in the brain.The assumed daily need is about 500 mg of pure choline (equivalent to about 4 eggs or ~15 g of lecithin powder), or twice as much for people with genetic polymorphisms (especially PEMT or MTHFR).What happens in case of overdose?Very high doses (more than 3.5 g/day) can cause fishy body odor (a sign of excessive TMA production), slight blood pressure drops, sweating, and even diarrhea or vomiting.One recent study found a correlation of Choline intake and the risk of type 2 diabetes. So the “more helps more” principle does not apply here either.And if I want to test anyway?Direct choline tests are rarely offered. There are some secondary biomarkers but they need to be interpreted correctly taking some factors into account. In this case, a genetic test especially for PEMT would be more insightful than blood work.8. Coenzyme Q10 – Mitochondrial CatalystWhy should I consider to supplement?Coenzyme Q10 is a vitamin-like compound essential for mitochondrial function, energy (ATP) production, lipid profile regulation, and cellular protection (as a fat-soluble antioxidant). The body’s own production declines with age – often along with energy levels.Note: If you take statins to lower cholesterol, you should strongly consider to supplement with Q10!There are two forms of Q10: Ubiquinone is cheaper, Ubiquinol possibly more effective. Some studies show better absorption with Ubiquinol, others no difference. Experts usually suggest using Ubiquinol with age to reduce the conversion burden.A usual dose is 100 to 200 mg daily – potentially more the older you get and short term after infections, injuries, or toxin exposure.What happens in case of overdose?Higher doses (above 300 mg) may occasionally cause sleep issues or stomach irritation.And if I want to test anyway?Not crucial, but nothing speaks against checking – except perhaps cost and effort. Personally, my Q10 level was surprisingly low after COVID-19, and I significantly increased my dose.9. Creatine – For Muscle Power and Brain PerformanceWhy should I consider to supplement?Creatine improves muscle strength, supports recovery, and boosts mental performance – especially in older adults or those on vegetarian diets.Usually, 5 grams per day are recommended. Recently, higher doses are being tested, e.g., to support cognitive function during sleep deprivation.What happens in case of overdose?Generally well tolerated. Very high doses can cause water retention or mild gastrointestinal discomfort. And: Creatine does not cause hair loss (for most people), as far as we currently know.And if I want to test anyway?Rare and not very meaningful.10. Taurine – Cell Protector for Heart and BrainWhy should I consider to supplement?Taurine regulates cell volume, calcium flow, and protects the heart and nervous system. Particularly beneficial in stress, sport performance, high blood pressure, blood sugar issues, or vegetarian diets – as it is almost absent from plant foods.In recent years, taurine has become a focus of longevity research, showing many benefits and virtually no side effects.Recommended dosages range from 500 mg up to 10 g daily.What happens in case of overdose?Taurine is considered very safe – even high doses are well tolerated in the long term. In sensitive individuals, very high doses may cause fatigue or blood pressure drops.And if I want to test anyway?Rarely done, but sometimes included in amino acid panels.Bonus: Micronutrients You Probably Need More Of – But Should Test FirstThe following nutrients are important and deficiencies are common, especially without supplementation. However, they also carry risks if overdosed. So here, more is not always better – testing or deeper consultation is worthwhile:Vitamin D – To reach toxic levels usually requires very high doses for a long time. But from values above 50 ng/ml, your calcium levels should be monitored, according to chinese government. Vitamin D tests are common and easy.Omega-3 – The optimal omega-3 index (blood test!) is 8–11%, so not unlimited. Too high levels may be linked to arrhythmias. Expert recommendations around 1.5 g DHA/EPA daily are likely safe and effective, but occasional testing of your index is advised.Selenium – A narrow margin: German soils are low in selenium, so deficiency is likely. The US is the opposite. Selenium is crucial not only for thyroid hormone conversion (T4 to T3), but also for a balanced immune response and protection against oxidative stress. Both deficiency and excess can be harmful – better test before supplementing!Iodine – Like selenium: deficiency is common in Germany, while Japan has very high dietary intake. The thyroid depends on iodine to produce hormones. But if your thyroid function is already out of balance (e.g. Hashimoto’s or hyperthyroidism), high-dose iodine could trigger flare-ups or worsen symptoms. Better test first and/or consult an expert!Conclusion:You don’t need to do a blood test for every supplement. But you should know what you’re doing – and why. With the ten micronutrients listed above, you can start with confidence. And if you're unsure about the "bonus" nutrients: a drop of blood or saliva can often bring more clarity than the fourth health podcast ;)