Biomarker lab tests typically take a biological sample, like blood, to evaluate certain biomarkers, which are measurable indicators of your health. Whether you’re checking your hormones, thyroid, or cholesterol levels, each test comes with its own special instructions.
Each test has its own processing time, after which you’ll receive your results either in the mail or in an online portal. If you receive an abnormal or unexpected result, you’ll want to follow up with a healthcare provider to discuss next steps, which may include medication, lifestyle changes, or additional testing.
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Key Takeaways:
Preparing properly for lab tests helps ensure your results are accurate and reliable.
Some tests — like fasting cholesterol or fasting glucose — require you not to eat or drink anything but water for a period of time, and others may need to be done at a specific time of day based on your body’s natural rhythms. Avoid drinking alcohol and caffeine, doing strenuous exercise, and smoking before most testing, as these can temporarily change your blood chemistry. Specifically, always follow each testing kit’s preparation directions.
Reading the instructions carefully, gathering supplies ahead of time, and mailing your sample promptly all help to keep the process smooth and stress-free.
Biomarker lab tests typically take a biological sample, like blood, to evaluate certain biomarkers, which are measurable indicators of your health. Whether you’re checking your hormones, thyroid, or cholesterol levels, each test comes with its own special instructions. Still, a few universal steps that apply to most lab tests help ensure the process goes smoothly and that your results are accurate.
In this guide, we’ll break down what most biomarker lab tests measure, how to prepare for them, and what to do once you receive your results.
Not appropriately preparing for or incorrectly performing a test can lead to inaccurate results, like false positives or false negatives. These results could lead to unnecessary worrying, missed information, or the need to retest.
Preparing properly, taking your time, and carefully following your test’s directions helps to reduce these risks and makes your results far more reliable.
Some common blood and lab tests might include specific directions, including:
Cholesterol and lipid panels (triglycerides). Some of these tests may need overnight fasting, especially if your clinician wants a fasting sample, so follow the specific instructions for your test.
Blood glucose tests. If you’re taking a fasting glucose test, then you’d be right to assume you’ll need to fast before taking it. That means avoiding any food or drink besides water for at least 8 hours before the test.
Hormone tests. Certain hormones, like testosterone, are typically measured in the morning when levels tend to peak. Conveniently, you can test your testosterone levels from home with Hims.
Nutrient level tests. For these tests, you might avoid certain supplements that could throw off your numbers.
If a blood test in question requires fasting, failing to do so can lead to inaccurate blood test results. This is because, after eating, the levels of certain substances in your blood naturally change. For instance, glucose levels rise after meals. Fasting before your test helps to reduce these fluctuations and provides more consistent results.
Besides glucose tests, you may need to fast before testing your cholesterol, triglycerides, and high-density lipoprotein (HDL) levels. Not every lab test requires fasting, so if you’re unsure, ask your healthcare provider or follow the instructions that come with your test. After you’ve completed your test, you can eat or drink something immediately.
Some lab and blood test prep involves setting your alarm clock. That’s because certain hormones and biomarkers rise and fall naturally throughout the day — a pattern known as circadian variation. For example, cortisol levels are highest in the morning, and testosterone and growth hormone also peak earlier in the day. Tests that measure these hormones can yield different results depending on when you collect your sample.
So, if your test requires a morning or late-night collection, take note. Research supports that collection timing makes a real difference, especially for hormones like cortisol, testosterone, and aldosterone.
As long as your test doesn’t expressly state you should avoid consuming any liquid, including water, hydrating before taking a lab test is important. That’s especially true for at-home tests that use a blood sample, whether via a finger-prick lancet or a Tasso® device. Water hydrates your veins, making them more accessible and encouraging better blood flow.
Just be sure to stick with plain water, as flavored water and sugary drinks might alter test results.
Some medications and supplements can interfere with lab results, either by directly affecting the test or by changing the levels of substances in your blood. For instance, blood pressure medications can alter hormone ratios, and certain antibiotics can make kidney function appear worse than it really is. Never stop, skip, or change how you take a prescription medication just to prepare for a lab test unless a healthcare provider tells you to.
Even over-the-counter products and herbal remedies can cause trouble, since their ingredients aren’t always clearly labeled. One example is biotin, which can interfere with several hormone and thyroid tests and sometimes lead to misleading results. If you take biotin, your healthcare provider or test instructions may recommend pausing it for a period of time before testing, so always check before making any changes.
According to the Centers for Disease Control and Prevention (CDC), even plain, unsweetened coffee can raise blood sugar because some people’s glucose levels are more sensitive to caffeine. Caffeine can also temporarily increase blood pressure and heart rate, which might affect certain cardiovascular readings.
Both coffee and alcohol can interfere with liver function tests, which often measure markers like total protein, albumin, and bilirubin, and enzymes such as aspartate aminotransferase (AST), alkaline phosphatase (ALP), and alanine aminotransferase (ALT).
Alcohol can also raise blood pressure, giving you another reason to skip happy hour before your test.
Thinking of hitting the gym before taking your lab test? Think again. Intense workouts can temporarily change your blood chemistry, raising levels of certain enzymes like creatine kinase (CK), ALT, AST, and bilirubin — the same markers used to check for liver or muscle issues. These shifts may happen because vigorous exercise can cause tiny muscle tears and temporarily affect liver blood flow.
Even a tough session of weight lifting or endurance training can lead to results that look like liver disease or muscle injury when everything’s actually fine. One study found that just two days of rest after strenuous exercise was enough to return these levels to normal. So, to get accurate results, it’s best to avoid heavy exercise for at least 48 hours before testing.
Smoking and vaping aren’t great for your health, and they can throw off your lab results, too. Research shows that smoking can increase red blood cell count, hemoglobin, and red cell size, along with content markers such as mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), plateletcrit (Pct), and red cell distribution width (RDW). It can also raise white blood cell (leukocyte) levels, particularly granulocytes and monocytes, which can make your results look abnormal even when you’re healthy.
Knowing how to prepare for blood work and lab tests can go a long way toward getting results you can trust. Small steps, like fasting when instructed, drinking plenty of water, and skipping caffeine, alcohol, and intense workouts, help your sample reflect your usual health — not just what you ate or did that day.
Regular lab testing makes checking in on your health simple and convenient, but preparation is what keeps those results meaningful. Take your time, follow each step carefully, and when in doubt, reach out to the testing company or your healthcare provider for guidance.
No. Many tests don’t require fasting, but sometimes certain tests do, like fasting glucose, cholesterol, and triglyceride panels. Always follow instructions provided by the lab, and if you are unsure, ask your healthcare provider for clarification before testing.
It depends on the test and the medication. Some medicines, including blood pressure medication, antibiotics, or supplements like biotin, can affect results. Always check your test instructions and, if necessary, talk to a healthcare provider before making any changes to your routine.
If you make a mistake, don’t panic. If you spill or underfill your collection sample, or you forget a step, contact the testing company’s customer support. Most will send a replacement kit or help you troubleshoot so you can retest correctly.
Turnaround time varies by test type and company, but most results arrive within a few days to a week after your sample reaches the lab. You’ll typically receive an email or text notification when they’re ready to view online.
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