Complement (C3, C4, CH50): Understanding Your Blood Test Series

1. Overview: What this test reveals and why it is important

The complement system is a cascade of more than 30 proteins that form a cornerstone of innate immunity. These proteins work in a carefully orchestrated sequence to:

· Opsonise pathogens for phagocytosis.

· Recruit and activate inflammatory cells via chemotaxis.

· Form the membrane attack complex (MAC) to lyse bacteria and infected cells.

· Clear immune complexes and apoptotic debris – a critical housekeeping function.

Three complement tests are commonly ordered in clinical practice:

· C3 and C4: The most abundant and routinely measured complement proteins. Their levels reflect both synthesis (primarily in the liver) and consumption during immune activation.

· CH50 (total haemolytic complement): A functional assay that measures the integrity of the classical pathway (C1–C9). It is the best screening test for inherited complement deficiencies.

Clinical utility:

· Assessing disease activity in systemic lupus erythematosus (SLE): Low C3 and C4 indicate classical pathway consumption by immune complexes, particularly in lupus nephritis. Serial monitoring guides treatment intensity.

· Diagnosing and monitoring complement‑consuming diseases: Mixed cryoglobulinaemia, vasculitis, membranoproliferative glomerulonephritis (MPGN), C3 glomerulopathy, and acute post‑streptococcal glomerulonephritis.

· Detecting inherited complement deficiencies: Low CH50 with normal C3 and C4 suggests deficiency of an early component (C1q, C2, C4). These patients are prone to recurrent infections and autoimmune syndromes.

· Diagnosing hereditary angioedema (HAE): Low C4 with normal C1q and C3 between attacks is characteristic of C1 inhibitor deficiency.

Important principle: Complement levels are dynamic biomarkers, not static diagnoses. They must be interpreted alongside clinical findings, other autoantibodies (anti‑dsDNA, cryoglobulins), and acute‑phase reactants (CRP, ESR).

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2. What does it measure

a. Units of measurement

· C3 and C4: Milligrams per decilitre (mg/dL) or grams per litre (g/L).

· CH50: Units per millilitre (U/mL) or percent of normal pooled plasma.

· Some laboratories also report C1q, factor B, properdin, and C1 inhibitor (quantitative and functional) for specific indications.

b. Normal Range

(Reference ranges vary by laboratory, assay method, and population; the following are general guidelines.)

Adults:

· C3: 75–175 mg/dL (0.75–1.75 g/L)

· C4: 14–40 mg/dL (0.14–0.40 g/L)

· CH50: 30–75 U/mL (assay‑dependent)

Children:

· Neonates: 50–120% of adult levels; mature by 6–12 months.

· Older children: Adult ranges.

Pregnancy:

· C3 and C4 increase by 10–30% due to oestrogen‑mediated hepatic synthesis. Do not use non‑pregnant reference ranges. Serial trends within the same pregnancy are more informative.

Interpretation notes:

· Low C3 and C4: Classical pathway activation – SLE, cryoglobulinaemia, MPGN type I, vasculitis.

· Low C3 with normal C4: Alternative pathway activation – C3 glomerulopathy, MPGN type II (dense deposit disease), post‑streptococcal GN, factor H/I deficiency.

· Low CH50 with normal C3/C4: Inherited deficiency of an early classical pathway component (C1q, C2, C4, C1 inhibitor).

· Low C4 with normal C3: Hereditary angioedema (between attacks); also seen in mixed cryoglobulinaemia.

· Elevated C3/C4: Acute‑phase response (infection, inflammation, tissue injury); non‑specific.

· Very low C3 and C4 with normal CH50: Rare; assay interference or paraproteinemia.

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3. Other factors connected to this

a. Direct correlation (factors that directly lower or raise complement)

Factors that lower complement (consumption or decreased synthesis):

· Immune complex‑mediated diseases:

· Systemic lupus erythematosus (SLE): Classical pathway activation; low C3 and C4 correlate with disease activity, especially nephritis.

· Mixed cryoglobulinaemia (type II/III): Predominantly low C4; C3 may be normal or low.

· Hypocomplementaemic urticarial vasculitis (HUVS): Low C1q, C4, C3.

· Membranoproliferative glomerulonephritis (MPGN): Type I – low C3 and C4; type II (dense deposit) – isolated low C3.

· Acute post‑streptococcal glomerulonephritis: Transient low C3, normal C4.

· Infective endocarditis, shunt nephritis, chronic osteomyelitis – persistent antigenaemia drives complement consumption.

· Autoantibodies against complement proteins:

· C3 nephritic factor (C3NeF): IgG autoantibody that stabilises C3 convertase, causing uncontrolled C3 consumption. Hallmark of C3 glomerulopathy.

· C4 nephritic factor: Rare; associated with MPGN.

· Inherited deficiencies:

· C1q, C2, C4 deficiency: Low CH50, low specific component, normal C3.

· C1 inhibitor deficiency (hereditary angioedema): Low C4 (consumed by uncontrolled classical pathway activation), normal C1q and C3 between attacks; during attacks, C2 and C4 are transiently very low.

· Factor H, factor I, properdin deficiency: Alternative pathway dysregulation; low C3.

· Decreased synthesis:

· Severe liver disease (cirrhosis, fulminant hepatic failure): All complement proteins are hepatically synthesised.

· Malnutrition / protein‑energy wasting.

· Plasmapheresis, large‑volume paracentesis – mechanical removal.

Factors that raise complement (acute‑phase response):

· Acute and chronic inflammation: C3 and C4 are acute‑phase reactants; levels rise in response to IL‑6, IL‑1, TNF‑α.

· Infections: Bacterial, viral, fungal.

· Tissue injury: Surgery, trauma, burns, myocardial infarction.

· Malignancy: Particularly solid tumours.

· Pregnancy: Physiological increase.

· Obstructive jaundice: Cholestasis elevates complement.

b. Indirect correlation (factors that influence interpretation or cause artefactual changes)

· Sample handling:

· Complement proteins are labile. Serum or plasma must be separated from cells within 2 hours of collection and stored at –70°C if not assayed immediately. Delayed processing or storage at room temperature causes falsely low results.

· Biotin interference:

· High‑dose biotin (>5 mg/day) can cause falsely low complement levels in streptavidin‑based immunoassays. Discontinue biotin ≥48 hours before testing.

· Haemolysis, lipaemia, hyperbilirubinaemia: May interfere with nephelometry and turbidimetry.

· Age: Neonates have lower levels; adult levels achieved by 1 year.

· Race/ethnicity: Some populations have genetically lower baseline C4 levels (e.g., null alleles for C4A or C4B).

· Medications:

· Immunosuppressants (corticosteroids, cyclophosphamide, mycophenolate, rituximab): Reduce complement consumption by suppressing disease activity; complement levels rise as disease improves.

· Eculizumab (anti‑C5): Blocks terminal complement pathway; does not affect C3/C4 levels but renders CH50 undetectable (therapeutic goal).

· ACE inhibitors, ARBs: No direct effect.

· Pregnancy: As above; use gestation‑specific reference ranges if available.

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4. Disorders related to abnormal values

a. When complement is low (clinically significant – consumption or deficiency)

Systemic lupus erythematosus (SLE):

· Prevalence: 50–70% of SLE patients have low C3 and/or C4 at some point.

· Correlation: Strongest with active lupus nephritis (Class III, IV, V). Rising anti‑dsDNA and falling C3/C4 herald renal flare.

· Serological remission: Normalisation of complement is a treatment goal.

Mixed cryoglobulinaemia:

· Type II (monoclonal IgM RF + polyclonal IgG) and type III (polyclonal IgM RF + polyclonal IgG):

· Low C4 is characteristic; C3 may be normal or low.

· Associated with hepatitis C virus (HCV), Sjögren’s syndrome, B‑cell lymphoproliferative disorders.

· Vasculitis: Palpable purpura, arthralgia, neuropathy, glomerulonephritis.

Membranoproliferative glomerulonephritis (MPGN) and C3 glomerulopathy:

· MPGN type I (immune complex‑mediated): Low C3 and C4.

· MPGN type II (dense deposit disease): Isolated low C3, normal C4; C3 nephritic factor positive in 80%.

· C3 glomerulonephritis: Low C3, normal C4; C3NeF often positive.

Acute post‑streptococcal glomerulonephritis (APSGN):

· Transient low C3, normal C4. Returns to normal within 6–8 weeks.

· If hypocomplementaemia persists beyond 8 weeks, reconsider diagnosis (MPGN, SLE, etc.).

Infective endocarditis / shunt nephritis:

· Persistent antigenaemia drives complement consumption; low C3 and C4.

· Complement normalises with effective antimicrobial therapy.

Hereditary angioedema (HAE):

· Type I (85%): Low C1 inhibitor protein and function; low C4 (between attacks), normal C1q and C3.

· Type II (15%): Normal or elevated C1 inhibitor protein but low function; low C4.

· Acquired angioedema (AAE): Low C1q, low C4, low C1 inhibitor; associated with lymphoproliferative disorders or anti‑C1 inhibitor autoantibodies.

Inherited complement deficiencies:

· C1q, C2, C4 deficiencies: Very low CH50, low specific component, normal C3. Increased risk of SLE‑like illness and encapsulated bacterial infections.

· C3 deficiency: Very low C3 and CH50; severe, recurrent pyogenic infections.

· Properdin deficiency (X‑linked): Impaired alternative pathway; increased risk of meningococcal disease.

· Factor H / factor I deficiency: Uncontrolled alternative pathway activation; low C3; predisposes to atypical haemolytic uraemic syndrome (aHUS) and C3 glomerulopathy.

b. When complement is high (acute‑phase response)

· Non‑specific: Infection, inflammation, tissue injury, malignancy, pregnancy.

· Isolated elevation with no other abnormalities: Usually benign; repeat if persistent.

· In SLE: High complement does not exclude active disease; some patients have normal or elevated levels despite active extra‑renal manifestations.

c. When complement is normal

· Does not exclude SLE or other immune complex diseases. Up to 30–50% of SLE patients have normal complement levels at any given time.

· Normal complement with high clinical suspicion: Pursue alternative diagnostic markers (anti‑dsDNA, anti‑Sm, anti‑Ro/SSA, cryoglobulins).

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5. Best way to address aberrant levels

Important principle: Low complement is not treated. The underlying disease – SLE, vasculitis, cryoglobulinaemia, glomerulonephritis, or infection – is treated. Complement levels normalise as the disease comes under control. There is no medication that directly raises complement levels (except in inherited deficiencies where specific replacement therapy exists).

a. Quick ways or using Medications

Treatment is disease‑specific and guided by rheumatology, nephrology, haematology, or immunology.

For systemic lupus erythematosus (SLE):

· Hydroxychloroquine (HCQ):

· Universal, first‑line, disease‑modifying. Reduces flares, improves survival, protects against renal damage.

· Contributes to gradual normalisation of complement over 3–12 months.

· Dose: 200–400 mg/day (≤5 mg/kg real body weight).

· Retinal toxicity: Annual ophthalmology screening.

· Corticosteroids:

· Prednisolone 0.5–1 mg/kg/day or methylprednisolone IV pulses (500–1000 mg/day for 3 days) for rapid control of severe flares.

· Complement levels begin to rise within 1–2 weeks; normalisation over 4–12 weeks.

· Immunosuppressants:

· Mycophenolate mofetil (MMF): 2–3 g/day – first‑line for lupus nephritis.

· Cyclophosphamide: IV pulses – for severe, proliferative nephritis; also for CNS lupus, severe vasculitis.

· Azathioprine: 2–3 mg/kg/day – maintenance therapy.

· Methotrexate: For refractory arthritis, cutaneous lupus; not for active nephritis.

· Complement normalisation occurs over 3–6 months.

· Biologics:

· Belimumab (anti‑BAFF): Reduces autoantibody production, flares, and steroid exposure; complement often normalises within 6–12 months.

· Rituximab (anti‑CD20): Off‑label for refractory lupus nephritis, severe haematological involvement. Effective in anti‑dsDNA‑positive, hypocomplementaemic patients.

For mixed cryoglobulinaemia:

· Treat underlying cause:

· HCV‑associated: Direct‑acting antivirals (DAAs) – viral eradication leads to complement normalisation over 3–6 months.

· Autoimmune / lymphoproliferative: Rituximab, immunosuppression.

· Rituximab: First‑line for severe cryoglobulinaemic vasculitis; rapidly reduces immune complexes and improves complement.

· Plasmapheresis: For severe, life‑threatening vasculitis (cryocrit >5%, progressive glomerulonephritis, mononeuritis multiplex).

For C3 glomerulopathy / MPGN with C3NeF:

· Supportive: BP control, ACE inhibitors/ARBs for proteinuria.

· Immunosuppression: Variable response; mycophenolate, corticosteroids may be tried.

· Eculizumab (anti‑C5): Terminal complement blockade; may stabilise renal function in some patients. CH50 becomes undetectable (therapeutic target), but C3 levels remain low.

For hereditary angioedema (HAE):

· On‑demand therapy:

· C1 esterase inhibitor concentrate (plasma‑derived or recombinant) – IV.

· Icatibant (bradykinin B2 receptor antagonist) – subcutaneous.

· Ecallantide (kallikrein inhibitor) – subcutaneous (USA only).

· Prophylaxis:

· C1 esterase inhibitor concentrate (IV or subcutaneous).

· Danazol (attenuated androgen) – increases C1 inhibitor synthesis; avoid in children, pregnancy, and men with prostate cancer. Side effects limit use.

· Lanadelumab (monoclonal anti‑kallikrein) – subcutaneous prophylaxis.

· C4 levels remain low between attacks despite prophylaxis.

For inherited complement deficiencies:

· No replacement therapy for most deficiencies (except C1 inhibitor in HAE).

· Vaccination: Immunise against encapsulated bacteria (S. pneumoniae, N. meningitidis, H. influenzae type b).

· Prophylactic antibiotics: Penicillin or amoxicillin for asplenic‑equivalent risk.

· Prompt treatment of infections.

· Eculizumab for aHUS – blocks terminal complement; patients must be vaccinated against meningococcus.

Do not self‑prescribe – all immunosuppressive and immunomodulatory therapies require specialist supervision.

b. Using Supplements or Holistic medicine

Supplements are adjunctive only; they do not replace disease‑modifying therapy. No supplement directly raises complement levels. The following support overall immune regulation and reduce disease activity in complement‑consuming diseases.

For supporting immune regulation in SLE / autoimmune disease:

· Vitamin D:

· Deficiency is universal in SLE and correlates with higher disease activity and lower complement.

· Supplementation reduces flares and improves outcomes.

· Preferred: D3 (cholecalciferol) from lichen.

· Dose: 600–2000 IU/day for maintenance; higher (2000–4000 IU/day) for deficiency correction, under guidance.

· Omega‑3 fatty acids (EPA/DHA):

· Anti‑inflammatory; reduces disease activity in SLE and may improve cardiovascular risk.

· Preferred source: Algae oil – sustainable, plant‑based, direct EPA/DHA, no marine contaminants.

· Avoid conventional fish oil (overfishing, ocean pollution, ethical concerns).

· Dose: 2–4 g/day EPA/DHA.

· Curcumin (turmeric):

· Inhibits NF‑κB, reduces pro‑inflammatory cytokines.

· Small studies suggest benefit in lupus nephritis.

· Use phytosomal, liposomal, or with piperine for bioavailability.

· Avoid products with added synthetic folic acid or cyanocobalamin.

· N‑acetylcysteine (NAC):

· Antioxidant, replenishes glutathione.

· Small RCT in SLE showed reduction in disease activity.

· Dose: 600–1200 mg/day.

· Green tea catechins (EGCG):

· Antioxidant, immunomodulatory.

· Use beverage (2–3 cups/day) rather than concentrated extracts (hepatotoxicity risk).

· Zinc:

· Essential for immune function; deficiency common in autoimmune disease.

· Preferred form: zinc picolinate or zinc citrate.

· Dose: 15–30 mg elemental zinc/day; monitor copper.

· Selenium:

· Antioxidant; may reduce autoimmune activity.

· Brazil nuts (1–2/day) or supplement 50–100 mcg/day as selenomethionine.

· Probiotics / prebiotics:

· Modulate gut microbiota; emerging evidence in SLE (reduced flares, improved serology).

· Preferred sources: fermented plant foods (kimchi, sauerkraut, kombucha, miso, tempeh); standardised probiotic supplements with documented strains.

· Vitamin B12 and folate:

· Use methylcobalamin and methylfolate – active forms, avoid synthetic folic acid and cyanocobalamin.

· Methotrexate‑treated patients require methylfolate, not folic acid.

· Dose if deficient: methylcobalamin 1000–2000 mcg/day, methylfolate 400–1000 mcg/day.

Supplements to AVOID:

· Echinacea, astragalus, alfalfa sprouts – theoretical immune stimulation; may exacerbate autoimmunity.

· High‑dose vitamin E – may impair immune function.

· Synthetic folic acid – avoid; use methylfolate.

· Cyanocobalamin – avoid; use methylcobalamin.

· High‑dose biotin – interferes with complement immunoassays; discontinue before testing.

· Unregulated herbal blends – hepatotoxicity risk; no proven benefit.

General caution: Supplements are adjunctive, not curative. Do not use without consulting rheumatologist/nephrologist.

c. Using Diet and Foods (following a plant‑forward, ecologically sustainable approach)

Diet is a cornerstone of managing systemic inflammation in complement‑consuming diseases. A well‑designed, nutrient‑dense, anti‑inflammatory plant‑based diet can complement medical therapy, reduce cardiovascular risk, and improve quality of life.

Core dietary principles – what to emphasise:

· Anti‑inflammatory dietary pattern:

· Mediterranean‑style plant‑forward diet – abundant vegetables, fruits, legumes, whole grains, nuts, seeds, olive oil.

· High in polyphenols, fibre, unsaturated fats, and antioxidants.

· Low in refined carbohydrates, added sugars, and saturated fats.

· Strong evidence for reduced inflammatory markers and improved outcomes in SLE.

· Adequate protein intake:

· Essential for hepatic synthesis of complement proteins in malnourished patients.

· Plant‑based protein sources (hierarchy adhered):

· Primary: legumes (lentils, chickpeas, beans, soy products – tofu, tempeh, edamame).

· Fungi / algae: mycoprotein (Quorn), spirulina, chlorella.

· Biotechnology: precision‑fermented dairy proteins (animal‑free whey, casein) – acceptable emerging options.

· Dairy / eggs: permitted but not emphasised; low‑fat fermented dairy (yoghurt, kefir) if tolerated.

· Meat, poultry, fish: deliberately omitted. Effective plant‑based alternatives exist to meet all nutritional requirements. There is no need for animal products to support health in complement‑consuming diseases.

· Omega‑3 fatty acids:

· ALA sources: ground flaxseeds, chia seeds, hemp seeds, walnuts.

· Direct EPA/DHA: microalgae (spirulina, chlorella – limited amounts); algae oil supplements for therapeutic doses.

· Polyphenol‑rich foods:

· Berries, green tea, dark chocolate (≥70% cocoa), extra virgin olive oil, turmeric, ginger, cruciferous vegetables (cooked), onions, garlic, apples, citrus.

· Vitamin D:

· Sunlight exposure; fortified plant milks; supplement from lichen if needed.

· Calcium:

· Critical for SLE patients on long‑term corticosteroids to prevent osteoporosis.

· Plant sources: fortified plant milks, calcium‑set tofu, tempeh, tahini, kale, bok choy, broccoli, okra, almonds.

· Iron:

· Anaemia of chronic disease is common; iron deficiency may occur with concurrent NSAID use or menorrhagia.

· Plant sources: lentils, chickpeas, tofu, pumpkin seeds, quinoa, fortified cereals, dark leafy greens (cooked).

· Enhance absorption with vitamin C; avoid tea/coffee with meals.

· Folate:

· Avoid folic acid‑fortified foods. Choose unfortified grains and products.

· Patients on methotrexate require methylfolate supplementation (see above).

· Natural folate sources: dark leafy greens, legumes, asparagus, beets, avocado, citrus fruits.

· Vitamin B12:

· No reliable plant‑based whole food source. Must be supplemented – methylcobalamin from fermentation, non‑animal, ecologically responsible.

· Fiber:

· High‑fibre diets (≥30 g/day) reduce systemic inflammation and support gut microbiome health.

· Sources: oats, barley, legumes, vegetables, fruits, nuts, seeds.

What to avoid or severely limit:

· Ultra‑processed foods, refined carbohydrates, added sugars – promote inflammation, insulin resistance, and dysbiosis.

· Excess sodium – hypertension is common in SLE and renal disease. Limit processed foods, canned goods, salty snacks.

· Trans fats – partially hydrogenated oils; pro‑inflammatory.

· Saturated fats – excess intake promotes inflammation; limit coconut oil, palm oil, butter, cream, cheese.

· Alcohol – may interfere with methotrexate metabolism, exacerbate hepatotoxicity; limit or avoid.

· Smoking – single most important modifiable risk factor for SLE disease activity, cardiovascular disease, and complement consumption. Cessation is essential.

Specific dietary considerations:

· Alfalfa sprouts: Contain L‑canavanine, which may activate SLE; avoid.

· Gluten: Only restrict if coexistent coeliac disease (more common in autoimmune disease) or documented non‑coeliac gluten sensitivity.

Lifestyle factors with proven benefit:

· Smoking cessation – as above.

· Sun protection – strict sun avoidance, protective clothing, high‑SPF broad‑spectrum sunscreen – critical for photosensitive SLE patients.

· Stress reduction – mindfulness, meditation, yoga, adequate sleep – stress triggers flares.

· Regular moderate exercise – improves fatigue, cardiovascular health, mood, bone density.

· Weight management – obesity worsens disease activity and cardiovascular risk.

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6. How soon can one expect improvement and the ideal time frame to retest

Complement normalisation reflects disease control and is a valuable therapeutic endpoint.

For SLE / lupus nephritis:

· Corticosteroids: Clinical improvement within days; complement begins to rise within 1–2 weeks; normalisation over 4–12 weeks.

· Mycophenolate / cyclophosphamide: Complement normalisation over 3–6 months; often lags behind clinical response.

· Belimumab / rituximab: Complement normalisation over 6–12 months.

For cryoglobulinaemia:

· HCV treatment with DAAs: Complement normalises over 3–6 months after viral clearance.

· Rituximab: Complement improves within 2–4 months.

For acute post‑streptococcal glomerulonephritis:

· C3 returns to normal within 6–8 weeks. Failure to normalise by 12 weeks suggests alternative diagnosis.

For infective endocarditis:

· Complement normalises within 2–4 weeks of effective antimicrobial therapy.

For hereditary angioedema:

· C4 remains low between attacks even with successful prophylaxis; do not repeat complement to monitor treatment.

Retesting interval summary:

· Active SLE / lupus nephritis: C3, C4, anti‑dsDNA, and urinalysis every 1–3 months.

· Stable SLE / remission: Every 6–12 months.

· Cryoglobulinaemia: Every 3–6 months until stable, then annually.

· C3 glomerulopathy / MPGN: Every 3–6 months depending on disease activity.

· Inherited complement deficiencies: No routine retesting; diagnosis is genetic/functional.

· Pregnancy in SLE: C3, C4 every 1–3 months depending on disease activity.

Do not retest complement more often than every 2 weeks – meaningful change does not occur faster.

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Conclusion

Complement proteins are the immune system's cleanup crew – they tag debris for disposal, puncture bacterial membranes, and orchestrate inflammation. When they are consumed faster than the liver can produce them, their falling levels signal that the immune system is locked in battle, overwhelmed by immune complexes, or genetically unable to maintain its defences.

Low C3 and C4 are not diagnoses; they are cries for help from a body engaged in autoimmune warfare. The cry comes from the lupus kidney, the cryoglobulinaemic vessel, the C3 glomerulonephritic glomerulus. The treatment is not to pour in more complement but to silence the guns: hydroxychloroquine, immunosuppressants, biologics, antivirals, or, in the case of inherited deficiencies, antibiotics and vaccines.

A plant‑based, ecologically responsible diet – rich in legumes, whole grains, nuts, seeds, and algae‑derived omega‑3s – provides the anti‑inflammatory nutritional foundation that supports patients with complement‑consuming diseases. It supplies the vitamin D to modulate immunity, the calcium to protect corticosteroid‑treated bones, and the antioxidants to combat oxidative stress. It avoids the synthetic folic acid that may interfere with methotrexate therapy and the pro‑inflammatory load of animal products. There is no requirement for meat; its displacement by plants is itself a therapeutic and ecological act.

Complement is a number – a concentration, a titre. The patient is a story of fatigue, arthritis, proteinuria, purpura, angioedema, and resilience. Listen to the patient, not the complement level – but when complement falls and the story fits, act swiftly, decisively, and with compassion.

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Note on dietary recommendations on this site:

For the sake of our environment we adhere to the following dietary preference hierarchy:

1. Plant‑based

2. Fungi / algae / fermented

3. Biotechnology / lab‑grown / cultures

4. Dairy / eggs

5. Meat / fish / poultry (only if no effective alternative exists)

Special notes for complement‑consuming diseases:

· Vitamin D: Choose D3 from lichen; deficiency is universal in SLE and worsens disease activity.

· Omega‑3: Choose algae oil over fish oil for sustainable anti‑inflammatory support.

· Folic acid: Avoid synthetic folic acid; use methylfolate, especially in patients on methotrexate.

· Iron: Correct iron deficiency with plant‑based sources and vitamin C; avoid haem iron supplements.

· Smoking cessation and sun protection: Not dietary, but the single most important interventions for reducing disease activity.

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