Why Your Normal Lab Results Can Still Leave You Feeling Fatigued
After months of fatigue, you finally see a doctor, and then your bloodwork comes back “within normal limits.” Your doctor offers a few options, but nothing in the results shows what’s wrong. So why do you still feel this way?
Part of the answer lies in what “normal” actually means on a lab report.
Where Normal Ranges Come From
Most reference ranges are built by testing a group of people considered healthy and setting the range to cover the middle 95% of their results. Few labs run these studies themselves. Most adopt a range published by the test manufacturer or in the medical literature, then confirm it works for their own equipment and patients. When your blood test results arrive, each number is listed next to that range for comparison.
This approach is good at catching disease. It also tells you whether your result looks like most other people’s. However, it doesn’t tell you whether your body is functioning at its best.
When the “Healthy” Group Isn’t So Healthy
There’s a second problem. The people used to build a blood result range haven’t always been as healthy as assumed. When researchers screened out people with hidden liver disease, the healthy upper limit for ALT (a liver enzyme) dropped 10 points in men and 11 points in women (1). Thyroid specialists made a similar argument about TSH, the standard thyroid screening test. They pointed out that older reference groups included people with undiagnosed thyroid problems, which tended to push the upper limit higher (2).
The Corrections
Since the original research, better technology and research into lab ranges have influenced the situation. This has led to updated medical guidelines. For example, in 2017 the American College of Gastroenterology recommended further evaluation of the liver at ALT levels previously considered normal (3). And in 2020, the American Gastroenterological Association raised the ferritin cutoff for diagnosing iron deficiency in people with anemia from 15 to 45 ng/mL (4). That’s a significant change. Ferritin results matter here because low iron stores are a common (and treatable) cause of fatigue.
Many labs, however, still print the older ranges on their reports. So, how a result is interpreted can matter as much as whether it falls within the given range.
Looking Beyond a Single Test
Thyroid testing shows how this scenario plays out. Most thyroid evaluations start with TSH, and if it’s within normal ranges, testing usually stops there. That’s a reasonable first step, but TSH doesn’t show everything about the thyroid. Some people with normal TSH have elevated thyroid antibodies, an early sign of autoimmune thyroid disease, or other changes that only appear on a fuller thyroid panel.
The same idea applies more broadly. A single result is a snapshot. Comparing results over time, looking for patterns, and comparing results to how you actually feel gives a far more complete picture than checking whether each number falls inside a range.
What’s Next?
If you’re frequently tired and your standard labs look normal, it’s worth asking a few questions, such as: “Where do my results fall within the relevant ranges? How do they compare with my past results? Are there tests that might tell us more?” A good healthcare practitioner will welcome those questions.
At TCIM, we take the time to look at the whole picture, including your history, your symptoms, and what your lab results mean for you specifically. If you’ve been told everything looks normal but you don’t feel normal, we’d be glad to take a closer look.
Learn more and contact us to schedule an appointment.
Sources:
1. Prati D, Taioli E, Zanella A, et al. Updated definitions of healthy ranges for serum alanine aminotransferase levels. Ann Intern Med. 2002 Jul 2;137(1):1–10. PMID: 12093239. Available from: https://pubmed.ncbi.nlm.nih.gov/12093239/
2. Wartofsky L, Dickey RA. The evidence for a narrower thyrotropin reference range is compelling. J Clin Endocrinol Metab. 2005 Sep;90(9):5483–8. doi:10.1210/jc.2005-0455. PMID: 16148345. Available from: https://pubmed.ncbi.nlm.nih.gov/16148345/
3. Kwo PY, Cohen SM, Lim JK. ACG Clinical Guideline: Evaluation of Abnormal Liver Chemistries. Am J Gastroenterol. 2017;112(1):18–35. doi:10.1038/ajg.2016.517. Available from: https://pubmed.ncbi.nlm.nih.gov/27995906/
4. Ko CW, Siddique SM, Patel A, et al. AGA Clinical Practice Guidelines on the Gastrointestinal Evaluation of Iron Deficiency Anemia. Gastroenterology. 2020;159(3):1085–1094. doi:10.1053/j.gastro.2020.06.046. Available from: https://www.gastrojournal.org/article/S0016-5085(20)34847-2/fulltext
The Temecula Center for Integrative Medicine is an Integrative Medical Clinic specializing in all aspects of Functional Medicine.
Our focus is solely on the treatment and prevention of chronic disease and we specialize in helping patients with serious, life-altering illnesses.
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Dr. Erik Lundquist is the founder and medical director for the Temecula Center for Integrative Medicine. He is a member of the American Holistic Medical Association as well as the Institute of Functional Medicine. He specializes in endocrine disorders especially thyroid and adrenal dysfunction, chronic fatigue, migraine headaches, cardiometabolic disorders, and chronic pain.
