Health & Fitness

Blood testing 101 – your most common questions answered

Let's decode blood testing and get answers to your FAQs. Expert advice on how to prepare, what to expect, and what results mean.

If you’re new to the world of blood testing it’s completely natural to have some questions about the process. Here you’ll find the answers to the most frequently asked questions, like what to expect and how to prepare to ensure accurate results.

Here’s what we cover:

  • how long blood tests take
  • what happens to your blood after the blood draw
  • what do blood tests measure
  • blood tests and biomarkers
  • how and when you’ll get your results
  • how to read blood test results
  • what to know about reference ranges
  • what biological and lifestyle factors can affect your results 
  • reliability and accuracy of test results
  • how results may be affected if you didn’t prepare properly for the test
  • how a COVID-19 infection or vaccine can influence results
  • how often to get a blood test
  • do you need a lab slip for a blood test
  • tips to reduce fainting during a blood test
  • how to share your results with your doctor

How long does a blood test take?

Good news: Hardly any time at all! A blood draw typically takes just a few minutes. At Aware, our medical team usually needs about 2–5 minutes to collect a sample.

If you’re nervous or afraid of blood tests or have a history of fainting, know that you’re not alone. Let our medical team know and we can go at your pace. We’ll make sure to give you as much time as you need to feel comfortable and have a smooth experience. You can also lie down if you prefer, just let us know.

How much blood will be drawn?

This depends on the specific blood test. Between 3–10 ml is usually enough for most blood tests.

Since our blood test at Aware measures dozens of biomarkers, we draw a bit more blood – around 15 ml, or 4 tubes of blood – that’s about one tablespoon. This makes up less than 0.3% of the total volume of blood circulating through the body – which is about 5 liters on average. 

When donating blood, most people can safely give around 500 ml of blood. In comparison, a few milliliters is quite little, and your body can reproduce the blood cells rather quickly. 

What happens to my blood after the test?

Your blood samples will go into test tubes labeled with your name. If you’re testing with Aware, they will be transported safely to our lab partner at a temperature between 15–25 °C.

For some tests, like the complete blood count, lab technicians test the blood as it is in the tube, measuring the amount and size of different blood components. For other tests, the tube goes first into a centrifuge (a spinning medical device) to separate the blood into composite parts (such as proteins).

Once testing is complete, the sample will be stored for up to 5 days in case a retest is necessary. After that, the blood is disposed of safely and hygienically.

What do (Aware) blood tests measure?

Blood is a rich source of data that can help you understand important areas of your overall health. Blood tests are an excellent screening tool that can give you a wealth of information about how well your body is functioning. They can be used to measure organ health, detect or monitor medical conditions such as diabetes or high cholesterol, track health trends over time and identify risks and problems before they even show up as symptoms.

At Aware, we prioritize preventive health and offer blood testing to help detect chronic inflammation and determine heart and metabolic health. We don't just measure one thing – we take a comprehensive approach with a curated list of markers to give you a detailed picture of your current health. Our tests examine key areas such as nutrient deficiencies, hormonal balance, inflammation, blood sugar control and cardiovascular health to identify areas that could use improvements to avoid long-term health risks.

Our health checks are designed to provide you with the data-backed insights you need to make informed decisions to live a longer, healthier life.

What are biomarkers?

Your body houses thousands of biomarkers, or biological markers (what we at Aware call “health markers”). These are molecules found in your blood, urine, saliva, and tissues that signal normal or abnormal processes happening in your body. Examples of biomarkers include cholesterol, blood pressure, and blood sugar. 

Measuring biomarkers helps detect, diagnose, and monitor health conditions. They can also signal how well the body is responding to treatment. Beyond that, biomarkers are an invaluable tool for preventive healthcare: They can determine someone’s chances of developing certain conditions in the future. Regular blood tests can catch potential warning signs early so you and your doctor or healthcare team can come up with a plan to protect your health.

How and when will I get my results?

If you get tested at a conventional lab or a doctor’s office, it may take several days or weeks to get your results, depending on the blood test and lab. They may come in the mail, or some offices require people to return in person to pick up the printed results.

At Aware, our goal is to make this experience as seamless for you as possible, which is why we deliver most results from blood tests within 24 hours and you can see them all conveniently inside your Aware App. If you get tested on a Friday or Saturday, you’ll get your results on Monday. We’ll reach out via email as soon as they’re ready. If you'd like to print out a paper copy of your results or share a PDF with your doctor, you can do so easily from within the app.

How do I read my blood test results?

Getting blood tests is easy.  But making sense of blood test results can be tricky because of the medical jargon involved. To help understand what the results mean, check out our full article on how to read blood test results. Knowing how to read them can be both useful and empowering, which will also help you make better decisions about your health.

If you have any questions or concerns about your results, it’s always best to ask your healthcare team or doctor to help explain what they mean, especially in context of your medical history and previous results. They can explain in more detail what they mean for your body and health.

If you’ve had an Aware blood test with us – and we hope you do – you can share your results in a PDF via email with your doctor or healthcare professional straight from the app. With the Aware App we want you to get a clearer picture of your health by storing all your lab results in one place and provide you with helpful, actionable content. You can find health facts and additional information on each biomarker, what high and low results may mean for health, and evidence-based strategies to keep biomarkers in range.

What are reference ranges? 

Reference ranges represent the “normal value” of a biomarker, and medical professionals consider this to be the healthy range based on a person’s age or sex. Typical test results from a large group of healthy people help healthcare practitioners determine the reference ranges for each biomarker. Chronic health conditions, certain medications, and various other factors can make test results fall outside the reference range.

What if my blood test result falls outside the reference range?

There are many factors that can influence your blood test results, such as stress, recent illness, or even something as simple as what you ate or drank before the test (read more about this in the next section). Additionally, while the reference range is a helpful guideline, it's important to remember that everyone's body is different, and some healthy individuals may fall outside of the normal range.

In fact, around 1 in 20 healthy people will have lab values outside the reference range while people with health conditions can have results in the normal range. 

It's also worth noting that one isolated out-of-range result doesn't always mean there is a problem because a blood test is a snapshot of your health status at a specific point in time. It’s important to interpret your lab tests in context with your medical and family history and look at patterns and trends over time with repeated testing. 

A test result outside the reference range may or may not indicate a problem, so it’s best to discuss it with your healthcare team or doctor. 

Can female hormones or menstruation affect blood test results?

Yes. Female sex hormones and other biomarkers can fluctuate significantly throughout the menstrual cycle, which can influence your test results. Some markers that can change during the cycle include:

  • iron
  • lipids (fats such as cholesterol)
  • hsCRP (a marker of inflammation)
  • vitamin D

As a general principle, it's best practice to always get blood tests at the same point in your cycle so you can compare your results and track changes over time. 

Will having COVID-19, or getting a COVID-19 vaccine affect my test results?

This depends on whether you have an active COVID-19 infection or if you’ve have recently been infected. If you’re still testing positive for the virus, it could affect your results. This is because levels of infection markers like leukocytes and their lymphocytes as well as CRP go up as a result of illness and injury. [Also, we kindly request you to self-isolate according to government guidelines and not to come into the Aware Lab while testing positive.

It takes most people with a healthy immune system around 1–3 weeks after an infection to develop antibodies to COVID-19. So we recommend waiting 3 weeks after testing negative before getting a blood test to get an accurate picture of your antibody levels.

If you’ve recently gotten the COVID-19 vaccine (within the last few days), you may have higher infection markers as your immune system reacts to the foreign invaders in the vaccine. After 3 weeks, your results will show your IgG antibody levels. If they’re high, you can rest assured your body is responding to the vaccine efficiently. If they’re low, you may need a booster vaccine. 

While high IgG levels don’t mean you’re totally immune to the virus, they reduce the chance of having a severe infection.

Can a keto diet affect blood test results?

Potentially, yes. Your diet affects numerous nutrient biomarkers in the blood, such as iron, potassium, calcium, lipids, glucose levels, and more.

The keto diet, in particular, has been shown to increase cholesterol levels, especially in the first weeks and months of adopting the diet. 

What other factors can affect blood test results?

Many things can affect blood test results, including:

  • The time of day: Body temperature, heart, and brain function, and the production of hormones like cortisol, testosterone, and estrogen follow a circadian (24-hour) rhythm, so they can shift throughout the day.
  • The season: Your vitamin D levels usually fluctuate throughout the year if you don’t live in a country with year-round sunshine.
  • Stress: Psychological stress can affect levels of metabolites, enzymes, and hormones such as cortisol and adrenaline. 
  • Age: As we get older, our bodies change, and so do our biomarker levels. For example, cholesterol tends to rise with age.
  • Genetics: Some people are genetically predisposed to having higher levels of certain biomarkers, such as iron or cholesterol. Regular testing and early detection can prevent negative long-term health impacts.
  • Biological sex: Males and females have different levels of certain blood biomarkers, such as hemoglobin. Because of blood loss through menstruation, females are more likely than males to develop anemia. 
  • Lab technique: Variations in equipment, environment, temperature, and the method of collecting, transporting, and storing blood samples can all potentially affect blood test results. That’s why we only use the highest quality standards at Aware and are extremely selective when choosing our partner labs. We work with the best labs in Germany, which are certified and accredited by DIN EN ISO 15189 and comply with guidelines published by the German Medical Association for Quality Assurance of Laboratory Medical examinations (RiliBÄK).
  • Biological factors: Menstruation, menopause, puberty, and pregnancy can all affect your hormone levels and minerals like iron.
  • When you last ate: Many blood tests require fasting for about 12 hours beforehand because food intake affects blood markers like glucose, cholesterol, and others, as does the specific type of food you ate.
  • Drinking coffee: Studies show that drinking coffee before a blood test can elevate cortisol levels (the stress hormone). 
  • Recent injuries or infections: Sickness and injury can raise CRP – an inflammation marker – and infection markers like lymphocytes and leukocytes.
  • Strenuous exercise: Exercise can raise inflammation markers like CRP and impact creatine kinase, cholesterol, LDH, and the white blood cell count.
  • Medications and supplements: Many common medications and supplements can alter results. For example, The U.S. Food and Drug Administration (FDA) warns that taking supplements containing Biotin (vitamin B7) may interfere with some common lab tests.

Medical professionals refer to these factors as “preanalytical” variables, and it’s important to take them into account when interpreting test results.

How accurate and reliable are test results?

Blood tests performed by certified labs generally deliver very accurate and reliable results. However, no test is 100% accurate.

Aware only works with certified and accredited German labs that meet the highest standards for equipment, personnel, and quality control by regulatory agencies. The German Medical Association's Guidelines for Quality Assurance of Laboratory Medical Examinations (RiliBÄK) are very strict and thorough, ensuring highly accurate results.

Factors such as the specific test being performed, the quality of the sample, and certain medical conditions can affect the accuracy of test results. Additionally, test results should be interpreted in the context of medical/family history and other personal health-related information.

Over time, repeat testing shows important trends and patterns that are more accurate than a single result.

How can I prepare for a blood test?

Check out our handy checklist of everything you need to do to prepare for your test to ensure you get accurate results. One of the most important things is to make sure you are well hydrated.

The questions we hear most often are:

Can I have coffee before a fasting blood test?

For comparable results, it’s best to only drink water before a fasting blood test. Although everybody responds differently to caffeine, even a single cup of black coffee may interfere with blood test results. For instance, coffee can affect glucose levels, particularly in those who have diabetes.

While the impact may not be huge, we recommend saving your cup of joe until after the blood draw so you can get consistent and reliable results from your tests.

What if I ate before a fasting blood test?

One of the most common mistakes people make before a blood test is to eat or drink a glass of  juice. This can affect a variety of biomarkers, including:

  • Glucose: Food and drinks can temporarily spike glucose levels which may lead to a false diagnosis of hyperglycemia (high blood sugar).
  • Total cholesterol: A high-fat meal may temporarily increase total cholesterol levels, a test used to assess heart disease risk.
  • LDL cholesterol: Food that’s high in fat can raise low-density lipoproteins (LDL), also known as "bad" cholesterol, which is used to assess heart disease risk.
  • HDL cholesterol: A high-fat meal may slightly decrease high-density lipoproteins (HDL), also referred to as “good cholesterol”.
  • Triglycerides: This is a type of fat in the blood that also helps assess heart disease risk. Eating before a test can make triglycerides go up.
  • Gamma-Glutamyl Transpeptidase (GGT): Even small amounts of alcohol 24 hours prior to the test can increase GGT levels, which are used to assess liver function and excess alcohol consumption.
  • Vitamin B12: This test is used to identify a potential vitamin B12 deficiency, and eating beforehand may lead to inaccurate results.
  • Iron: Your body absorbs iron very quickly from food, so fasting is important to get an accurate measurement, and to check for an iron deficiency or anemia.

If you forgot to fast before your blood draw and are unsure if the test required fasting, let the medical team know. You may decide to reschedule your appointment, though this isn’t always necessary. Food and drinks may not have a significant impact on some biomarkers, and the effect may vary from person to person.

Can I exercise before a fasting blood test? 

Doing an intense workout in the 24 hours before a blood draw can impact your results and elevate inflammatory markers like CRP as well as other biomarkers such as creatine kinase, cholesterol, LDH, and white blood cell count.

However, everyone’s body reacts differently to exercise depending on genetics, fitness levels, and other factors. For some people, it may be fine to take a test after high-intensity physical activity. But just to be safe and get most accurate results, avoid high-intensity exercise the day before your blood test.

Can I drink alcohol before a blood test?

Drinking alcohol can affect some blood test results, including blood sugar, fat levels, as well as some liver enzymes. 

However, alcohol affects everyone differently depending on factors like age, sex, weight, how much you drink, and when you last ate. So, it may be possible to have some alcohol the day before a test without significantly affecting your results. 

Speak to your doctor or a member of the medical team about the best time to take your test, and drink plenty of water before your blood draw. 

Can I smoke before a blood test?

It’s generally not recommended to smoke before a fasting blood test as it can affect some results. In general, nicotine can increase blood sugar levels, leukocytes including neutrophils, lymphocytes,  monocytes, and other markers.

How often should I get a blood test?

When it comes to health, there’s no one-size-fits-all approach. The ideal frequency for your blood tests will depend on your individual health status, which is affected by your age, sex, genetics, medications, your family medical history, and your unique health goals. Consult a healthcare practitioner to find out what’s best for you.

Here are some general guidelines to consider:

  • Get a routine checkup and blood test 1–2 times per year to stay on top of your health.
  • People with pre-existing conditions like hypertension, heart disease, thyroid issues, anemia, diabetes, or PCOS may need more regular checkups (every 3–6 months or so). Speak to your doctor for individual advice. 
  • When starting treatment for a chronic condition, doctors may do more frequent testing (every few weeks) to see how it’s working.  
  • To track progress from changes to your nutrition, workout routine, stress management, sleep hygiene, or supplements, it’s recommended to test specific markers every 3–6 months.

Do I need to get a lab slip to get a blood test?

Typically, yes. For most labs you’ll need to get a lab slip from a healthcare professional to get a blood test.

But the good news is that you DON’T need a prescription or doctor’s note for a blood test with Aware. 

With Aware, you can directly book an appointment that best suits you in our app, and pop into our state-of-the-art lab in Berlin Mitte. Within 24 hours your test results will be available in-app  and if you like you can also share a PDF version of your results straight from your phone.

What to do if you faint during a blood test?

Fainting during a blood test is not uncommon, and is usually brought on by a fear of needles or the sight of blood. So if you have a history of fainting or you have a condition that makes you more likely to pass out, there are few steps you can take:

  • Inform the team: Let the medical team know before your blood draw that you have a tendency to faint so they can reassure you and guide you slowly through the process. If, at any point, you have the feeling that you’re about to faint, please alert the team right away.
  • Don’t watch: Avoid looking at the needle going into your arm. You can distract yourself by listening to relaxing music or having a friend by your side for the blood draw.
  • Lie down: If you feel lightheaded or dizzy, lie on your back with your feet elevated. This increases blood flow to your head and can help prevent fainting.
  • Take deep breaths: You can try counting slowly to 10 or practice box breathing to slow your heart rate and prevent fainting. 
  • Loosen any tight clothing: Make sure that your clothing isn’t constricting blood flow.
  • Drink some water: Hydrating helps bring your blood pressure back to normal.
  • Eat some sugar afterwards: Once the blood draw is over, have some sugar, such as a piece of fruit or a glass of juice, to raise your blood sugar levels and restore energy to your brain.
  • Take it easy: Avoid exerting yourself on the day following your test, especially in hot weather.

How can I share my Aware test results with my doctor?

It’s a good idea to keep your doctor in the loop about your blood tests, and the Aware App makes it super easy for you to share your results directly with them. We keep your health data confidential, and won’t share it with anyone without your consent. If you’d like to share your results, you can do this from 2 places in your app:

  • To share your most recent blood tests results: On the home screen, tap the share icon to the right of “Your results are in!”.
  • To share any past blood test results: Tap the profile icon in the top right of the home screen to go to your account. Under “Your appointments”, you’ll see the dates of all of your Aware blood tests and can tap the share icon on the right.

You can choose how you wish to share the PDF of your results – via email, Whatsapp, SMS, or Slack. 

As you get more blood tests with Aware, you can track your progress over time. This can help you and your doctor see how any changes you make (such as with medication, nutrition, or exercise) are working for your body.

Keep in mind that the results and explanations that you see inside your app are not a diagnosis. If a result concerns you or you’re curious to know more, please visit your doctor or healthcare team to talk about what this means for your individual health.

The bottom line

Blood tests are a widely used and key aspect of modern and preventive healthcare. They help healthcare practitioners detect issues before symptoms develop so you can treat and manage conditions before they become a problem. 

There are many different blood tests that measure various biomarkers in the blood to check overall health and detect specific conditions, such as heart issues, metabolic syndrome, or thyroid dysfunction. 

Many things can affect blood test results, including age, sex, hormone cycles, how you prepared for the blood draw, and other factors. 

Keep in mind that a blood test gives a snapshot of your health status at a particular moment in  time. With repeat testing, you can build a comprehensive picture of your health status, track your progress, and utilize the most reliable health data to optimize your well-being. Discuss your test results with your doctor, as they can help recommend treatments or lifestyle changes based on your personal medical history. 

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