The short answer
Yes, and biotin is the clearest case. Biotin (vitamin B7) can make certain lab tests read falsely high or falsely low without anything changing in your body, because many hospital analysers use biotin as part of the test itself. In a 2017 JAMA study, 10 mg of biotin a day for one week distorted 9 of 23 biotin-based tests [1]. Vitamin C can hide glucose and blood in a urine dipstick [12][13]. The fix is simple: tell the lab, and time your dose.
How can a supplement change a test result without changing your health?
There are two different ways, and they need different responses. A supplement can change the real level of something in your blood, which the test then measures correctly, or it can interfere with the chemistry of the test, so the machine reports a number that is not true. Biotin is the textbook example of the second kind.
The first kind is ordinary physiology. Creatine raises creatinine, the marker doctors use to estimate kidney function, because creatine breaks down into it. The number is real, but it does not mean what it usually means. We covered that in detail in Is creatine only for athletes?, so it gets only a short section here.
The second kind is analytical interference. Nothing is wrong with you and nothing is wrong with your kidneys, thyroid or heart; the test simply reads the wrong answer. That is the more dangerous of the two, because a result that looks clean and precise gives no hint that it is false. The European Thyroid Association lists biotin, next to antibodies and genetic variants, among the causes of thyroid results that do not match the patient [7].
Why does biotin distort some blood tests?
Because many automated immunoassays use biotin as a molecular hook. The test attaches biotin to an antibody and uses streptavidin, a protein that grips biotin extremely tightly, to pull that antibody out of the sample. Free biotin from a supplement competes for the same grip, and the analyser then miscounts [1].
This design works well as long as the blood contains only the tiny amount of biotin a normal diet provides. Unsupplemented blood holds roughly 0.12 to 0.32 ng/mL of biotin [8]. The lowest known interference threshold on the most sensitive tests is 10 ng/mL [3], which is far above diet but within reach of a high dose supplement.
Why can the same supplement make one result too high and another too low?
It depends on how the test is built. In a sandwich immunoassay, used for large molecules such as TSH and troponin, excess biotin blocks the capture step, so the signal drops and the result reads falsely low. In a competitive immunoassay, used for small molecules such as free T4, less signal means a higher result, so the same biotin reads falsely high.
The JAMA study measured exactly this split. After 7 days of 10 mg biotin, 5 of 8 biotin-based competitive tests (63 percent) read falsely high and 4 of 15 biotin-based sandwich tests (27 percent) read falsely low, while none of the 14 tests without biotin chemistry were affected [1].
| Test design | Typical examples | Direction of the error with excess biotin | Why it matters |
|---|---|---|---|
| Sandwich immunoassay | TSH, troponin, PTH | Falsely low | A low TSH looks like an overactive thyroid; a low troponin can hide heart muscle damage |
| Competitive immunoassay | Free T4, free T3, total T3 | Falsely high | High thyroid hormones next to a low TSH mimic Graves' disease |
| Assays without biotin chemistry | Many other platforms and methods | No biotin effect | Retesting on another platform is how labs expose the problem |
Which tests are affected by biotin?
The tests at greatest risk are thyroid and reproductive hormone tests, cardiac tests such as troponin, and tests for immunosuppressive drugs, according to a 2019 best practice review by laboratory specialists. The same review counts 92 cases of suspected biotin interference reported to the US Food and Drug Administration since 2016 [5].
In the JAMA study the list of affected analytes also included parathyroid hormone, prolactin, NT-proBNP, 25-hydroxyvitamin D, PSA and ferritin on at least one platform [1]. A study of 13 adults taking 10 mg a day for 8 days found significant changes in TSH, free T4 and total T3 on one widely used platform and a falsely low thyroglobulin on another, with the biggest effect 2 hours after the dose [2].
Whether your own test is affected depends on the platform and even the reagent lot your laboratory uses.
Can biotin make a thyroid test look like Graves' disease?
Yes. A falsely low TSH combined with falsely high free T4 and T3 is the exact laboratory pattern of an overactive thyroid. In a New Zealand case, markedly abnormal thyroid results normalised after biotin was stopped far faster than the half-life of T4 allows, which is the signature of assay interference rather than disease [15].
One Dutch case shows what is at stake. A 64-year-old man taking high dose biotin was referred with apparent Graves' disease and started on antithyroid medication. The laboratory results did not respond, he developed symptoms of an underactive thyroid caused by the treatment itself, and only then did the team find the biotin. After he stopped it, his thyroid tests normalised [10].
Why is a falsely low troponin the result that worries labs most?
Troponin is the blood test used to detect damage to heart muscle, so a falsely low value can make a heart attack look like something else. The EU medicines committee names "false negative troponin test results in patients with myocardial infarction taking biotin" explicitly in its 2019 warning text [6].
Manufacturers have responded. A 2026 Mayo Clinic study compared lots of one widely used troponin T test labelled free of biotin interference up to 20 ng/mL with newer lots labelled free up to 1200 ng/mL [11]. That tolerance is sixty times higher, and it shows the risk is shrinking where laboratories have switched, not that it has gone everywhere.
How much biotin does it take to cause a problem?
Most of the published interference comes from doses of 10 mg a day and higher, which is roughly 140 to 290 times the 35 to 70 µg a normal diet provides [8]. Dietary biotin intake does not typically push blood levels over the interference thresholds of laboratory tests, according to the 2019 best practice review [5]. The 10 mg dose in the JAMA study was chosen because it is common in over-the-counter products [1].
At the far end, patients with progressive multiple sclerosis were trialled on 300 mg a day, and their plasma biotin reached between 31.7 and 1160 µg/L (the same as ng/mL) [14]. At those levels most streptavidin hormone tests on the platform studied were affected.
| Source of biotin | Amount per day | What is known about lab interference |
|---|---|---|
| Ordinary Western diet | 35 to 70 µg [8] | Does not typically reach interference thresholds [5] |
| EU labelling reference (NRV) | 50 µg | The 100 percent line on an EU supplement label |
| EU medicines threshold for a warning | 150 µg per oral dose unit [6] | Medicines at or above this must warn about lab tests |
| Our B-complex | 300 µg per capsule | No published measurement at this dose that we could find; above the EU medicines warning threshold |
| Common over-the-counter high dose products | 10,000 µg [1] | Interference shown in 9 of 23 biotin-based assays at 10,000 µg [1] |
| Trial dose in multiple sclerosis | 300,000 µg | Most streptavidin hormone tests affected [14] |
Two things are honest to say about the middle of that table. We found no study that measured blood biotin after a 300 µg dose, so we cannot tell you it is safe for every assay, and we will not claim it. What we can say is that it is 33 times below the 10 mg dose behind most of the evidence, and 6 times the NRV.
How common is high blood biotin in Europe?
Much less common than in the United States, on current data. In a US emergency department, 7.4 percent of 1,442 patient samples had biotin at or above 10 ng/mL, the lowest known interference threshold [3]. A Dutch hospital laboratory that measured routine samples with mass spectrometry found only 0.2 percent above that level [4].
The Dutch authors still concluded it is "by no means a rare phenomenon": a laboratory of their size can expect biotin positive samples every day, with an impact that depends on the platform it uses [4].
How long should you stop biotin before a blood test?
There is no single official number, because the right gap depends on the dose, your kidney function and how sensitive the lab's test is [9]. For supplements up to 10 mg a day, a gap of roughly 8 to 10 hours is considered enough for most tests; at 300 mg a day it can take up to 73 hours [8].
Blood biotin peaks about 1.5 hours after a dose and has an average half-life of around 15 hours [9], and the thyroid study saw the strongest interference 2 hours after intake [2]. That makes the morning dose before a morning blood draw the worst possible timing. Kidney disease slows clearance, so the gap may need to be days rather than hours [8].
Our practical reading for a low dose product like our own: take your last capsule the morning of the day before the test, have the blood drawn, and take the next capsule afterwards. That gives more than a full day of clearance and avoids the peak the studies flag. For products in the milligram range, ask the laboratory, because some tests need a longer pause.
Why do EU medicines warn about biotin while supplements do not?
Because the warning was imposed through medicines law, and supplements are not medicines. In January 2019 the EU's Pharmacovigilance Risk Assessment Committee concluded that oral medicinal products containing 150 µg or more of biotin per dose unit can interfere with laboratory tests, and required their leaflets to say so [6].
The required leaflet text tells patients to inform their doctor or the laboratory before testing, that results may be falsely raised or falsely low, and that "multivitamins or supplements for hair, skin, and nails could also contain biotin" [6]. So the regulator itself points at supplements, but it can only write the obligation into medicine leaflets.
Some review articles describe this as a warning that "must accompany any biotin supplements" above 150 µg [9]. We read the original decision, and it is addressed to marketing authorisation holders of medicinal products [6]. A food supplement with the same amount of biotin carries no equivalent legal duty to warn. That gap is the reason this article exists.
Where does our own B-complex sit?
Our Vitamin B-Complex contains 300 µg of D-biotin per daily capsule, which is 600 percent of the NRV. That is twice the 150 µg level at which an EU medicine would have to print a lab test warning [6]. We are saying it here plainly because our label, as a supplement, is not required to.
That does not mean the capsule will distort your results. It means we cannot promise it will not, on every platform, and the cautious course costs nothing. If you take our B-complex and have a blood test coming up, tell the person taking the sample and skip that morning's capsule, as described above. The same applies to any multivitamin, hair or nail product you use alongside it, because the biotin adds up.
None of our other products lists biotin on its label. Our creatine monohydrate is relevant for a different reason, covered below.
Which other supplements change a measured result?
Two are well documented and common: vitamin C, which interferes with urine dipsticks, and creatine, which raises the kidney marker creatinine for a real physiological reason. Both are easy to handle once the person reading the result knows you take them.
Does vitamin C affect a urine test?
Yes, and at ordinary doses. Vitamin C interferes with the colour reactions many urine dipsticks use for glucose and blood, which gives false negative results [12][13]. When volunteers took 100 mg of oral vitamin C, or fruit juice, their urine already held enough to cause false negative dipstick results for haemoglobin and glucose [12].
In a multicentre study of clinical urine samples, vitamin C was present in 18.1 percent overall and 23.1 percent of people attending medical check-ups. When it was present, 42.3 percent of glucose results, 10.6 percent of haemoglobin results and 8.2 percent of leukocyte esterase results were false negatives [13]. Our Magnesium 7 in 1 contains vitamin C too, so mention it before a urine test. Some dipsticks include a vitamin C pad that flags the problem [12].
Does creatine raise creatinine?
Yes, modestly, and this one is a real change rather than a test error. Creatine converts to creatinine in the body, so serum creatinine can rise slightly while measured kidney filtration stays unchanged in healthy people. We explain the trials in Is creatine only for athletes?. Tell whoever reads your kidney panel that you take creatine.
What should you tell the lab or your doctor?
Tell them every supplement you take, by name and dose, and when you last took it. The European Thyroid Association lists a review of medications and supplements, "especially biotin", as a key step whenever thyroid results do not fit the patient, and recommends repeating the test after the suspected agent is stopped [7].
This matters because patients often leave supplements out. Laboratory reviews note that people may not realise a hair or nail product contains biotin at all [5], and that many do not mention supplements because they do not see them as treatment [9]. The interactions article makes the same point for medicines.
If a result surprises you or your doctor, a retest after a biotin pause, or on a different analyser, is the standard way to settle it [5]. It is quicker and cheaper than treating a condition you do not have. For the separate question of which markers are worth ordering in the first place, see which blood markers are worth checking.
Frequently Asked Questions
Does a normal multivitamin interfere with blood tests?
Usually not. A laboratory review states that multivitamins with the usual 30 µg of biotin will not distort any assay [9], and dietary biotin intake does not typically reach interference thresholds [5]. The published problems come from products around 10 mg and above [1]. If a multivitamin contains more than 150 µg, treat it like a biotin supplement and mention it.
How long before a blood test should I stop taking biotin?
For supplements up to 10 mg a day, about 8 to 10 hours is considered enough for most tests, while 300 mg a day can need up to 73 hours [8]. Kidney disease lengthens that. For a low dose product, taking your last dose the morning before the test day is a simple, cautious rule. For higher doses, ask the laboratory.
Can biotin cause a false heart attack test result?
It can make a troponin result falsely low, which risks missing a heart attack rather than inventing one. The EU requires medicines with 150 µg or more of biotin per oral dose unit to warn about exactly this [6]. Newer reagent lots tolerate far more biotin, up to 1200 ng/mL on one widely used troponin T test [11].
Is biotin interference dangerous for my health?
The biotin itself is not the risk; the wrong decision based on a false number is. Documented harms include patients treated for an overactive thyroid they did not have, one of whom developed an underactive thyroid from the unnecessary treatment [10]. Telling the lab about your supplements prevents almost all of it.
Should I stop my B-complex before a blood test?
Skipping the capsule on the morning of the test is a sensible precaution, because our B-complex contains 300 µg of biotin, twice the level at which EU medicines must carry a lab test warning [6]. Take it again after the blood draw. There is no nutritional cost to missing a single day.
The Bottom Line
A supplement can change a lab result in two ways: by changing what is really in your blood, as creatine does with creatinine, or by fooling the test, as biotin does in streptavidin immunoassays and vitamin C does in urine dipsticks. The second kind is the one to plan for, because a false result looks exactly like a true one.
The EU makes medicines with 150 µg of biotin or more carry a warning. Supplements carry no such duty, so we are telling you directly: our B-complex holds 300 µg per capsule. Skip it the morning of a blood test, name every supplement to the person who orders or reads it, and ask for a retest if a result does not fit how you feel. This article is general information, not medical advice.
Sources
- Li D, et al. Association of Biotin Ingestion With Performance of Hormone and Nonhormone Assays in Healthy Adults. JAMA, 2017.
- Ylli D, et al. Biotin Interference in Assays for Thyroid Hormones, Thyrotropin and Thyroglobulin. Thyroid, 2021.
- Katzman BM, et al. Prevalence of biotin supplement usage in outpatients and plasma biotin concentrations in patients presenting to the emergency department. Clinical Biochemistry, 2018.
- IJpelaar A, et al. Prevalence of detectable biotin in The Netherlands in relation to risk on immunoassay interference. Clinical Biochemistry, 2020.
- Bowen R, et al. Best practices in mitigating the risk of biotin interference with laboratory testing. Clinical Biochemistry, 2019.
- European Medicines Agency, PRAC. PRAC recommendations on signals adopted at the 14-17 January 2019 PRAC meeting (section 1.1, Biotin: interference with clinical laboratory tests). 2019.
- Campi I, et al. 2026 ETA guideline on interference in immunoassay measurements used in assessment of thyroid function. European Thyroid Journal, 2026.
- Balzer AHA, Whitehurst CB. An Analysis of the Biotin-(Strept)avidin System in Immunoassays: Interference and Mitigation Strategies. Current Issues in Molecular Biology, 2023.
- Ghazal K, et al. Hormone Immunoassay Interference: A 2021 Update. Annals of Laboratory Medicine, 2022.
- van den Berg R, et al. Apparent thyrotoxicosis in a patient with multiple sclerosis: biochemical assay interference due to high dose biotin use. Nederlands Tijdschrift voor Geneeskunde, 2018.
- Karon BS, et al. Analytical outlier rates for Roche fifth generation cardiac troponin T stat using biotin sensitive and insensitive reagent lots. Clinical Biochemistry, 2026.
- Brigden ML, et al. High incidence of significant urinary ascorbic acid concentrations in a west coast population: implications for routine urinalysis. Clinical Chemistry, 1992.
- Lee W, et al. The influence of vitamin C on the urine dipstick tests in the clinical specimens: a multicenter study. Journal of Clinical Laboratory Analysis, 2017.
- Piketty ML, et al. High-dose biotin therapy leading to false biochemical endocrine profiles: validation of a simple method to overcome biotin interference. Clinical Chemistry and Laboratory Medicine, 2017.
- Elston MS, et al. Factitious Graves' Disease Due to Biotin Immunoassay Interference: A Case and Review of the Literature. Journal of Clinical Endocrinology and Metabolism, 2016.
This article is for general information and does not replace advice from your doctor or laboratory. Food supplements are not a substitute for a varied and balanced diet and a healthy lifestyle.
