"Normal" Bloods, Not Normal Symptoms
What standard tests can miss
So your GP said your bloods are normal, but something inside you still doesn’t feel quite right. This is something that I hear so often in the clinic: "My GP said my bloods are all normal." Sometimes there’s a shrug, sometimes there’s frustration, and there’s almost always the same undertone: but why do I still feel like this?
I’ll let you in on a not so little secret.. What's considered "normal" on a pathology report isn't the same as what's optimal for you. Reference ranges are built by testing a broad population and taking the middle 95% of results. They are designed to screen for disease, not to tell you whether you're a thriving picture of health. They also don't always shift for the life stage you're in, even though your body's needs change enormously through puberty, pregnancy, postpartum and perimenopause.
So a result can sit inside the "normal" box and still be missing the full story. Here are three examples that can often be missed in a standard blood test:
Iron: your ferritin looks fine but you still feel wrecked
Ferritin is your iron storage marker, but it's also what's called an acute phase reactant. This means it rises as part of the body's inflammatory response. Iron is fuel that pathogens can also use, so your body deliberately locks it away in storage when there's inflammation happening anywhere, such as gut issues, autoimmune activity, a lingering infection, even high training load or chronic stress. A hormone called hepcidin does the locking, restricting how much iron gets released or absorbed. The result: ferritin can look "normal"on a blood test (or even high), but in reality your tissues are still starved of iron.
This is why ferritin should never be interpreted alone (but often is). Ideally we want to see it alongside C-reactive protein (CRP), a marker that confirms if inflammation is skewing the picture, haemoglobin (a protein that carries oxygen in your blood to tissues, it needs iron for production, so low haemoglobin is indicative of anaemia), transferrin (the protein that transports iron in the blood, eg: the number of taxis on the road), and transferrin saturation (the amount or transferrin protein bound to iron, eg: how many people are in the taxis). Together, these measures tell us whether you're genuinely iron-replete or whether inflammation is hiding a deficiency.
B12: serum levels are normal but the symptoms don’t add up
B12 is essential for nerve function, energy production, red blood cell formation and DNA synthesis. Deficiency shows up as fatigue, brain fog, tingling, mood changes and more. The problem is that standard serum B12 measures total B12, including a large inactive fraction that your cells can't actually use. Only the active fraction, holotranscobalamin, or "active B12", is taken up by your cells, which makes it a more accurate reflection of your true B12 status. Studies comparing the two have found active B12 to be a more sensitive and specific marker of deficiency than total B12, but it isn’t always the first test requested by your GP.
Thyroid: TSH alone isn’t actually testing your thyroid function
Your thyroid regulates metabolism, energy, temperature, mood and cognitive function, which is why thyroid dysfunction and postpartum depletion or perimenopause symptoms can look almost identical (fatigue, weight change, brain fog, low mood, feeling cold). Women are affected by thyroid conditions at far higher rates than men, and the prevalence of both overt and subclinical hypothyroidism rises notably through late perimenopause and postmenopause compared with the premenopausal years. Subclinical hypothyroidism, often driven by autoimmune thyroiditis, is already common in women during their reproductive years and frequently emerges or worsens through the menopause transition.
Most people don’t realise that a standard TSH test doesn't actually measure your thyroid. It’s obvious in the name of the test: thyroid stimulating hormone, which actually measures how hard your brain is signalling to your thyroid to produce thyroid hormones. It's a communication marker, not a function marker. Your thyroid can be under-functioning while TSH still sits in range, especially early on. To truly understand thyroid function, we want to see a full panel: TSH, free T3, free T4, and ideally thyroid antibodies (TPO and thyroglobulin) because autoimmune thyroid disease can be present well before TSH moves outside the reference range, and catching it early changes how we support you.
The wrap up
"Normal" tells us you don't have an obvious red flag. It doesn't tell us whether your body has what it needs to feelgenuinelywell. This is exactly why we take a collaborative, multidisciplinary approach at Papaya, because getting to the bottom of "I don't feel right" usually means looking wider than one test in isolation.
If this sounds familiar, let's have a proper look together. We recommend starting with a Clinical Nutrition or Naturopathy consultation to start the investigation.
Online booking available here.
This article is for general education only and not a substitute for personalised medical advice.
References:
Blumenthal NJ, Byth K, Eastman CJ. (2016). Prevalence of thyroid dysfunction and thyroid antibodies in a private obstetrical practice in Sydney. Aust N Z J Obstet Gynaecol. Jun;56(3):307-11. https://doi.org/10.1111/ajo.12462
Bondu JD, Nellickal AJ, Jeyaseelan L, Geethanjali FS. (2020). Assessing Diagnostic Accuracy of Serum Holotranscobalamin (Active-B12) in Comparison with Other Markers of Vitamin B12 Deficiency. Indian J Clin Biochem. 2020 Jul;35(3):367-372. https://doi.org/10.1007/s12291-019-00835-y
Dastidar R, Sikder K. (2022). Diagnostic reliability of serum active B12 (holo-transcobalamin) in true evaluation of vitamin B12 deficiency: Relevance in current perspective. BMC Res Notes. Oct 22;15(1):329. https://doi.org/10.1186/s13104-022-06224-8
Dignass A, Farrag K, Stein J. (2018). Limitations of Serum Ferritin in Diagnosing Iron Deficiency in Inflammatory Conditions. Int J Chronic Dis. Mar 18;2018:9394060. https://doi.org/10.1155/2018/9394060
Empson M, Flood V, Ma G, Eastman CJ, Mitchell P. (2007). Prevalence of thyroid disease in an older Australian population. Intern Med J. Jul;37(7):448-55. https://doi.org/10.1111/j.1445-5994.2007.01367.x
Ginzburg YZ. (2019). New diagnostic tools for delineating iron status. Hematology Am Soc Hematol Educ Program. Dec 6;2019(1):327-336. https://doi.org/10.1182/hematology.2019000035
Medicine Today: Interpreting Pathology Tests: https://medicinetoday.com.au/system/files/pdf/medicine_today/article/MT2014-11-064-PHILLIPS.pdf
Timbrell NE. (2024). The Role and Limitations of the Reference Interval Within Clinical Chemistry and Its Reliability for Disease Detection. Br J Biomed Sci. Feb 28;81:12339. https://doi.org/10.3389/bjbs.2024.12339
