Scientists reviewed 15 studies to understand how blood test results vary between different ethnic groups. They found that standard “normal” ranges for blood tests were mostly created using people from Western countries, which doesn’t work well for everyone else. The research shows that factors like genetics, diet, and environment cause real differences in blood markers like cholesterol, vitamin B12, and hormone levels across different populations. This matters because using the wrong “normal” range could lead to missed diagnoses or unnecessary treatments, especially for people in Africa, India, and Southeast Asia. The study calls for creating ethnic-specific normal ranges to make healthcare fairer and more accurate for everyone.

The Quick Take

  • What they studied: Whether blood test “normal” ranges are the same for all ethnic groups or if they need to be different based on a person’s background
  • Who participated: 15 research studies involving people from multiple ethnic backgrounds, including populations from Africa, India, and Southeast Asia that are often left out of medical research
  • Key finding: Blood test results vary significantly between ethnic groups. For example, cholesterol levels, vitamin B12, and hormone levels showed meaningful differences, suggesting that one-size-fits-all normal ranges don’t work for everyone
  • What it means for you: Your blood test results might be labeled “abnormal” when they’re actually normal for your ethnic background, or vice versa. This could lead to unnecessary treatments or missed diagnoses. Talk to your doctor about whether your results should be interpreted differently based on your background

The Research Details

This was a systematic scoping review, which means researchers carefully searched through thousands of published studies to find ones that compared blood test results across different ethnic groups. They looked at studies published up until December 2024 in major medical databases like PubMed, Embase, Scopus, and Web of Science. Starting with 4,514 articles, they narrowed it down to 15 studies that met their specific criteria—studies that actually measured blood markers in people from different ethnic backgrounds and compared the results. Two researchers independently reviewed each study to make sure they were selecting the right ones, which helps prevent mistakes. They used a framework called the Population-Concept-Context (PCC) method to decide which studies to include, focusing only on observational studies (studies that watch and measure rather than test interventions).

This approach is important because it gives us a complete picture of what we currently know about ethnic differences in blood tests. Rather than relying on one study, a scoping review pulls together evidence from many studies to identify patterns and gaps. This helps doctors and researchers understand whether current blood test standards are fair and accurate for all populations, or if they’re biased toward certain groups

The study followed strict guidelines from the Joanna Briggs Institute, which is a respected organization that sets standards for this type of research. Two independent reviewers checked the work to reduce errors. However, the review only found 15 studies that met their criteria out of over 4,500 articles, which shows there’s actually very little research on this topic. The fact that many ethnic groups are underrepresented in the research itself is a major finding—it means we don’t have enough information about blood test variations for many populations around the world

What the Results Show

The review found clear evidence that blood test results vary across ethnic groups in ways that matter for diagnosis. Lipid profiles (cholesterol and related fats), vitamin B12 levels, and anti-Mullerian hormone (a hormone related to fertility) showed the most notable differences between ethnic groups. These weren’t tiny differences—they were significant enough that using the same “normal” range for everyone could lead to wrong conclusions about a person’s health. The researchers discovered that current standard reference ranges, which are the “normal” values doctors use to interpret blood tests, were mostly created using Western populations. This means they don’t accurately represent what’s normal for people from other ethnic backgrounds. The studies included in this review looked at multi-ethnic populations, meaning they compared results across different groups living in the same or similar areas, which helps show that the differences are real and not just due to different living conditions.

Beyond the main findings, the review highlighted that research on this topic is unevenly distributed. There’s much more research on some ethnic groups than others, and many populations—particularly in Africa and parts of Asia—are severely underrepresented in the scientific literature. This gap in research means we don’t fully understand how blood test results vary for billions of people worldwide. The review also noted that genetic factors, environmental factors (like altitude or climate), and lifestyle factors (like diet and physical activity) all contribute to these variations, making the situation more complex than just having different normal ranges for different groups.

This review builds on growing awareness in medicine that one-size-fits-all approaches don’t always work. Previous research has hinted at ethnic differences in various health markers, but this systematic review is one of the first to comprehensively look at how widespread this problem is across multiple blood markers. The findings support what many doctors in diverse communities have suspected: that standard reference ranges don’t always fit their patients. This research validates concerns that have been raised about health inequities and the need for more inclusive medical standards

The biggest limitation is that only 15 studies met the inclusion criteria, which is a small number for drawing broad conclusions. Many of these studies were small or focused on specific populations, so the results might not apply everywhere. The review also found that some ethnic groups and regions have almost no research at all, making it impossible to know if there are important variations we’re missing. Additionally, the studies included used different methods and measured different biomarkers, making it hard to directly compare results. The review couldn’t determine exactly how much of the variation is due to genetics versus environment versus lifestyle, so we don’t fully understand the ‘why’ behind the differences

The Bottom Line

Healthcare providers should consider ethnic background when interpreting blood test results, especially for lipid profiles, vitamin B12, and hormone levels (moderate confidence). Patients should discuss their ethnic background with their doctor and ask if their results should be interpreted using population-specific ranges rather than generic ones (moderate confidence). More research is urgently needed to establish proper reference ranges for underrepresented populations (high confidence). Healthcare systems should work toward developing and implementing ethnicity-specific reference ranges (moderate confidence)

This matters most for people from African, Indian, and Southeast Asian backgrounds, as well as other non-Western populations. It’s particularly important for people who get results labeled as ‘abnormal’ but feel fine, or who have family members with similar results. Healthcare providers, especially those serving diverse communities, should pay attention to this research. People with chronic conditions that require regular blood monitoring should definitely discuss this with their doctors. However, this doesn’t mean you should ignore your doctor’s interpretation—it means you should have a conversation about whether your specific background should affect how your results are understood

This isn’t about seeing benefits over time—it’s about getting accurate diagnosis right now. The real timeline is how long it takes for healthcare systems to update their reference ranges, which could take years. In the meantime, having conversations with your healthcare provider about your background is something you can do immediately

Want to Apply This Research?

  • Track your blood test results over time with notes about your ethnic background and any health conditions. Record the specific values (not just ’normal’ or ‘abnormal’) and compare them to your previous results to see your personal patterns, rather than just comparing to standard ranges
  • When you get blood test results, use the app to document your ethnic background and any relevant lifestyle factors (diet, exercise, stress). This creates a personalized health record that you can discuss with your doctor to determine if standard ranges apply to you or if your results should be interpreted differently
  • Set up long-term tracking of key markers mentioned in this research (cholesterol, vitamin B12, thyroid-stimulating hormone, creatinine) and review them annually with your healthcare provider. Use the app to flag any results that seem inconsistent with how you feel, which could indicate that standard ranges aren’t appropriate for you

This review discusses research about how blood test normal ranges may vary by ethnic background. It is not medical advice. Blood test interpretation should always be done by a qualified healthcare provider who knows your complete medical history and can consider your individual circumstances. Do not change any medications or treatments based on this information. If you have concerns about how your blood test results were interpreted, discuss them with your doctor. This research highlights the need for more inclusive medical standards but does not change current clinical practice guidelines. Always follow your healthcare provider’s recommendations for your specific situation.