Sarah, the colleague I wrote about in the thyroid article, didn't just have hypothyroidism. She had Hashimoto's thyroiditis. An autoimmune condition where the immune system produces antibodies that attack the thyroid gland, gradually destroying it.
The distinction matters. Hypothyroidism is a description (your thyroid is underactive). Hashimoto's is an explanation (your thyroid is underactive because your immune system is attacking it). The treatment is the same (levothyroxine), but the diagnosis opens a different conversation. Autoimmune conditions don't usually come alone. They cluster. And knowing you have one changes how vigilantly you should screen for others.
Sarah's GP tested her thyroid antibodies after her TSH came back at 14. Anti-TPO was significantly elevated, confirming the autoimmune mechanism. Her GP then mentioned something that surprised both of us: people with autoimmune thyroid disease have a higher-than-average risk of coeliac disease, type 1 diabetes, and other autoimmune conditions. Not a certainty, but a statistical association that warrants awareness and, in some cases, screening.
That conversation is why I'm writing this as the final article in a thirty-part series. Autoimmune disease connects nearly everything I've covered: thyroid, gut health, fatigue, inflammation, iron deficiency, brain fog, skin problems, hair loss, joint pain. It's a lens through which many of the individual articles in this series link together. And it's one of the most underdiagnosed categories of disease in Australia.
A note before we get into it
General information only. I'm not a rheumatologist or an immunologist. Autoimmune disease diagnosis and management require specialist expertise. Blood tests screen for autoimmune markers, but they don't replace specialist clinical assessment, imaging, or biopsy.
If you suspect you have an autoimmune condition, work with your GP to initiate investigation and obtain appropriate referrals.
What autoimmune disease actually is
Your immune system is designed to distinguish between "self" (your own cells) and "non-self" (pathogens, foreign substances). In autoimmune disease, this distinction breaks down. The immune system produces antibodies that attack your own tissues, as if your body were a foreign invader.
The specific tissue targeted determines the condition. Attack the thyroid: Hashimoto's or Graves' disease. Attack the gut lining in response to gluten: coeliac disease. Attack the joints: rheumatoid arthritis. Attack the pancreatic beta cells: type 1 diabetes. Attack multiple organ systems: lupus (SLE).
There are over 80 recognised autoimmune conditions. Collectively, they affect an estimated 4-8% of the population, with women disproportionately affected (roughly 75% of autoimmune disease occurs in women). They're among the top ten leading causes of death in women under 65.
The common thread: the immune system is overactive, misdirected, and causing damage to the body's own tissues. The specific symptoms depend on which tissue is being attacked, but the underlying mechanism is shared.
Why diagnosis takes so long
This is the part that matters most if you're reading this article and wondering whether autoimmune disease might explain your symptoms.
The average time from symptom onset to autoimmune diagnosis is estimated at 4-5 years. Some studies report longer. The reasons are systemic.
Symptoms are nonspecific. Fatigue, joint pain, brain fog, skin changes, hair loss, digestive issues, mood changes. These are the hallmarks of autoimmune disease. They're also the hallmarks of stress, poor sleep, nutritional deficiency, ageing, and a dozen other things. Unless a clinician specifically considers autoimmunity, the symptoms are easily attributed to more common causes.
Symptoms fluctuate. Autoimmune conditions often follow a relapsing-remitting pattern, flaring and then settling. This inconsistency makes it harder to build a clinical case and easier to dismiss symptoms as transient.
No single test diagnoses most autoimmune conditions. Unlike, say, a fasting glucose for diabetes, there's no single definitive blood test for most autoimmune diseases. Diagnosis typically requires a combination of symptoms, blood markers, imaging, and sometimes biopsy.
Patients see multiple doctors. Because symptoms span multiple systems (joints, skin, gut, energy), patients often see different specialists for different complaints. None of them see the full picture.
Women are disproportionately dismissed. Research consistently shows that women's symptoms are more likely to be attributed to stress, anxiety, or psychosomatic causes. Since autoimmune disease predominantly affects women, this bias directly delays diagnosis.
Blood testing is often the entry point that changes the trajectory. A positive thyroid antibody test, a positive coeliac screen, an elevated CRP in someone with chronic fatigue and joint pain. These results shift the conversation from "maybe it's stress" to "let's investigate further."
The blood markers that point toward autoimmunity
Thyroid antibodies (anti-TPO, anti-Tg)
What they detect
Antibodies against thyroid peroxidase (anti-TPO) and thyroglobulin (anti-Tg). These are the two most common markers of autoimmune thyroid disease (Hashimoto's and Graves').
Why they matter
Elevated thyroid antibodies confirm that abnormal thyroid function is autoimmune in origin. This changes the clinical outlook. Hashimoto's is progressive (the thyroid will continue to decline over time), and the presence of one autoimmune condition increases the probability of others.
Who should test
Anyone with confirmed thyroid dysfunction (elevated or suppressed TSH), a family history of autoimmune thyroid disease, or unexplained thyroid-adjacent symptoms alongside other autoimmune features.
Detailed coverage: Thyroid article
Coeliac antibodies (tTG-IgA)
What they detect
Tissue transglutaminase IgA (tTG-IgA), the primary screening antibody for coeliac disease.
Why they matter
Coeliac disease is the most underdiagnosed autoimmune condition in Australia, affecting approximately 1 in 70 Australians, with 80% remaining undiagnosed (Coeliac Australia). Screening is a blood test that can change a life, given the long-term complications of undiagnosed coeliac (malnutrition, osteoporosis, increased cancer risk, fertility problems).
Critical requirement
You must be eating gluten when you test. Gluten-free diets produce false negatives.
Detailed coverage: Gut health article
CRP and ESR (inflammation)
What they detect
C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) are nonspecific markers of systemic inflammation. They don't identify the cause, but they confirm that an inflammatory process is present.
Why they matter
Persistently elevated CRP or ESR in someone with autoimmune-suggestive symptoms (fatigue, joint pain, skin changes, fever) strengthens the case for specialist referral and further investigation. They're also used to monitor disease activity in known autoimmune conditions.
Full Blood Count
What it reveals
FBC can show signs consistent with autoimmune disease: anaemia (common in many autoimmune conditions), low white blood cells or platelets (suggestive of lupus or other conditions), and elevated inflammatory markers.
ANA and specialist markers
ANA (Antinuclear Antibodies)
The primary screening test for systemic autoimmune diseases, particularly lupus (SLE). A positive ANA means the immune system is producing antibodies against components of cell nuclei. However, ANA is not specific. It can be positive in healthy individuals, in infections, and in other conditions. A positive ANA warrants specialist interpretation, not panic.
Other specialist markers
Anti-dsDNA (lupus-specific), anti-CCP (rheumatoid arthritis), ENA panel (mixed connective tissue diseases), and complement levels (C3, C4) are typically ordered by specialists, not as first-line screening.
ANA testing is NOT available through Bloody Good. It's a specialist-ordered test that requires clinical context for interpretation. If your GP suspects a systemic autoimmune condition, they'll order it as part of the investigation.
Autoimmune conditions that cluster together
One of the most clinically important features of autoimmune disease is clustering. Having one autoimmune condition increases your risk of developing another. Common clusters include:
Hashimoto's thyroiditis + coeliac disease. The association is well-documented. Estimates suggest 2-5% of people with Hashimoto's also have coeliac disease, significantly higher than the general population rate. Screening for coeliac is reasonable in anyone diagnosed with autoimmune thyroid disease.
Type 1 diabetes + autoimmune thyroid disease + coeliac disease. This triad is common enough to have its own screening protocol in paediatric type 1 diabetes management. Adults with type 1 diabetes should also be screened for thyroid and coeliac disease.
Autoimmune thyroid disease + pernicious anaemia. Pernicious anaemia (autoimmune destruction of the cells that produce intrinsic factor, causing B12 malabsorption) is more common in people with autoimmune thyroid disease. If you have Hashimoto's and unexplained B12 deficiency despite adequate intake, pernicious anaemia should be considered.
Rheumatoid arthritis + Sjogren's syndrome. These commonly coexist, with dry eyes and dry mouth accompanying joint inflammation.
If you're diagnosed with one autoimmune condition, ask your GP whether screening for associated conditions is appropriate. The clustering isn't a certainty, but awareness enables earlier detection.
What Bloody Good can screen for, and what needs specialist referral
Bloody Good can screen for:
Thyroid antibodies (anti-TPO) through the thyroid function panel. Coeliac antibodies (tTG-IgA) through the coeliac antibody test. Inflammatory markers (CRP, hs-CRP) through standalone or comprehensive panels. Full Blood Count through standalone or comprehensive panels. Nutritional markers that may suggest autoimmune-related malabsorption (iron, B12, folate, vitamin D).
What requires GP or specialist ordering:
ANA (antinuclear antibodies), anti-dsDNA, anti-CCP, ENA panel, complement levels (C3, C4), specific antibody panels for individual autoimmune conditions, rheumatoid factor, and HLA typing (e.g., HLA-DQ2/DQ8 for coeliac genetic testing).
Blood tests through Bloody Good serve as the screening layer, identifying markers that suggest autoimmune involvement and flagging the need for specialist investigation. They don't replace the specialist diagnostic pathway, but they can accelerate entry into it.
Who should be testing
Anyone with a diagnosed autoimmune condition. Screening for associated conditions is prudent (e.g., coeliac screening in Hashimoto's patients).
Anyone with a first-degree relative who has an autoimmune condition. Genetic predisposition increases risk.
Women with persistent, unexplained, multi-system symptoms: fatigue plus joint pain plus skin changes plus gut issues, particularly if they wax and wane.
Anyone with unexplained nutritional deficiencies, particularly iron, B12, and vitamin D that don't respond to supplementation (suggesting malabsorption from autoimmune gut damage).
Anyone with thyroid dysfunction that hasn't been characterised. If you know your TSH is abnormal but thyroid antibodies haven't been checked, it's worth adding.
Anyone who's been told "it's just stress" repeatedly without adequate investigation.
How to prepare
For coeliac antibodies: You MUST be eating gluten (equivalent to 2-4 slices of bread daily for at least 6 weeks before testing). This is the most common testing error.
For inflammatory markers (CRP): Don't test during acute illness, recent injury, or infection. These produce transient elevations that confuse the picture.
For thyroid antibodies: No specific preparation needed. Can be tested alongside standard thyroid function.
For iron, B12, vitamin D: Standard preparation as covered in previous articles.
Tests to consider through Bloody Good
Autoimmune screening panel
Thyroid Function Test (TFT)
Includes TSH, Free T4, Free T3; some panels include anti-TPO.
Test it with Bloody Good:
Product: Thyroid Function Test (TFT)
Coeliac Antibodies Blood Test
tTG-IgA screening (must be on gluten).
Test it with Bloody Good:
Product: Coeliac Antibodies Blood Test
High-Sensitivity CRP
Systemic inflammation marker.
Test it with Bloody Good:
Product: High-Sensitivity CRP Blood Test
Full Blood Count (FBC)
Anaemia, immune markers, and baseline blood health.
Test it with Bloody Good:
Product: Full Blood Count (FBC) Blood Test
Nutritional markers that suggest autoimmune malabsorption
Iron Studies (Including Ferritin)
Unexplained iron deficiency may point toward coeliac disease.
Test it with Bloody Good:
Vitamin B12
Unexplained B12 deficiency may suggest pernicious anaemia or coeliac disease.
Test it with Bloody Good:
Product: Vitamin B12 Blood Test
Vitamin D (25-OH)
Low vitamin D may indicate malabsorption or an inflammatory process.
Test it with Bloody Good:
Product: Vitamin D (25-OH) Blood Test
Folate
Depleted alongside B12 and iron, folate deficiency may signal a gut absorption issue.
Test it with Bloody Good:
Product: Folate Blood Test
Comprehensive coverage
The Bloody Good Test covers 100 biomarkers including thyroid, inflammatory markers, FBC, iron, B12, folate, vitamin D, liver, kidney, and metabolic markers. Pairing this with a standalone coeliac antibody test provides the broadest screening coverage available.
What to do after testing
If thyroid antibodies are elevated: You have autoimmune thyroid disease (most likely Hashimoto's if TSH is elevated, Graves' if TSH is suppressed). Your GP will manage thyroid replacement and may recommend screening for associated autoimmune conditions, particularly coeliac disease.
If coeliac antibodies are positive: See your GP for gastroenterologist referral. Diagnosis is typically confirmed with duodenal biopsy. Do NOT start a gluten-free diet before biopsy, as it can produce false-negative results.
If inflammatory markers are elevated alongside multi-system symptoms: Your GP should consider specialist referral. Rheumatology if joint involvement is prominent, gastroenterology if gut symptoms dominate, dermatology if skin is the primary concern. The specialist will order targeted antibody panels (ANA, anti-CCP, etc.) that guide specific diagnosis.
If nutritional markers show a malabsorption pattern: Investigate the gut. Coeliac screening is a priority. If coeliac is negative, consider other gut pathology (Crohn's, pernicious anaemia, SIBO).
If everything's normal: Reassuring. The most common autoimmune conditions have been screened. If symptoms persist, discuss further investigation with your GP. Some autoimmune conditions are seronegative (antibody-negative) and require clinical diagnosis.
Thirty articles later
This is the thirtieth and final article in a series I started writing because I got my own blood tested and was surprised by what I found.
Over thirty articles, I've told you about every character in my life who taught me something about blood testing. My ferritin of 28. My vitamin D of 41. My ALT of 52. My dad's cholesterol, pre-diabetes, cardiovascular risk, and PSA conversation. My girlfriend's iron infusion, PCOS diagnosis, fertility fears, hair loss, and skin. Tom's B12 deficiency. Sarah's Hashimoto's. My mate's ferritin of 19 after years of training. My mum's post-menopausal cholesterol and borderline thyroid. A young colleague's cystic acne. A friend's LDL explosion on keto.
None of these stories were dramatic. Every single one was a quiet discovery, something that blood testing revealed before symptoms forced the issue.
The message has been the same from Article #1 to Article #30: blood testing isn't about finding something wrong. It's about understanding where you stand so you can make decisions with data instead of guessing.
Get tested. Save your results. Compare over time. Talk to your GP about what the numbers mean for you.
And if you're not sure where to start, start with The Bloody Good Test. One blood draw. One hundred biomarkers. One baseline to build on.
Browse all Bloody Good blood tests
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General information only. This article is not medical advice and is not a substitute for care from a qualified health professional. If you have concerning symptoms or urgent health issues, seek medical attention promptly.