Factor VIII Activity Blood Test: What High and Low Results Mean
Other names: Factor VIII Activity, Factor 8 Activity, FVIII Activity, Factor VIII Activity Clotting, Factor VIII Activity, Clotting, Factor VIII:C, Factor VIII:C Activity, FVIII:C, Coagulation Factor VIII Activity, Coag Factor VIII Activity, Factor VIII Coagulant Activity, Assay of Factor VIII Coagulant Activity, Factor VIII Assay, Factor 8 Assay, Factor VIII Activity Assay, Factor 8 Activity Assay, Factor VIII Activity Test, Factor 8 Activity Test, Factor VIII Activity Level, Factor VIII Level, Factor VIII Clotting Activity, Factor VIII Clotting Assay, Factor VIII C Activity, Factor VIII C Assay, Factor VIII C Level, Factor VIII Act, Factor VIII Activated QN, Factor VIII Activated, QN, FVIII Activity, FVIIIa, Factor VIII Activity High, High Factor VIII Activity, Elevated Factor VIII Activity, Elevated Factor 8 Activity, Factor VIII Activity Normal Range, Factor VIII Normal Range, Factor 8 Normal Range, Factor VIII High, Factor VIII High Meaning, Factor 8 High, Factor 8 Activity High, Factor VIII Activity Low, Low Factor VIII Activity, Factor VIII Activity Low Meaning, Factor VIII Deficiency, Hemophilia A Factor VIII, Antihemophilic Factor, Antihemophilic Factor VIII, Factor V111 Activity (common misspelling), Factor V111 High (common misspelling), Factor VIIII (common misspelling)
Optimal Result:
56 - 140 %.
QUICK ANSWER
Factor VIII Activity measures a clotting protein essential for blood clot formation. Normal range: 50–150% (most labs).
High Factor VIII = increased clotting risk. Low Factor VIII = increased bleeding risk (hemophilia A spectrum). These have opposite clinical meanings.
| Factor VIII Activity result | Interpretation |
|---|---|
| Below 1% | Severe hemophilia A — major spontaneous bleeding risk |
| 1–5% | Moderate hemophilia A |
| 5–40% | Mild hemophilia A — bleeding after surgery or trauma |
| 40–50% | Below normal — may indicate mild Factor VIII deficiency or VWF disorder |
| 50–150% | Normal range |
| Above 150% | Elevated — increased thrombotic (clotting) risk |
| Above 200% | Significantly elevated — persistent elevation warrants clinical evaluation |
Common questions at a glance:
| Question | Short answer |
|---|---|
| Is Factor VIII 180% dangerous? | Usually not if it is a single reading during illness — persistence matters more than a one-time result |
| Can pregnancy raise Factor VIII? | Yes — levels commonly reach 150–300% by the third trimester |
| Can the birth control pill raise Factor VIII? | Yes — estrogen-containing OCPs raise Factor VIII, which is part of the reason they increase VTE risk |
| Does high Factor VIII mean cancer? | Usually no — acute illness, pregnancy, and estrogen are far more common explanations |
| Should I repeat the test if it is high? | Yes — a repeat test 6–8 weeks after any acute illness gives a more accurate baseline |
WHAT DOES HIGH FACTOR VIII ACTIVITY MEAN?
High Factor VIII activity (above 150%) means the blood has more clotting protein than normal — which increases the tendency of blood to clot inappropriately. This is the opposite of hemophilia A.
High Factor VIII raises thrombotic risk, not bleeding risk. Persistent elevations above 150% have been associated with a substantially increased risk of venous thromboembolism (VTE), including deep vein thrombosis (DVT) and pulmonary embolism (PE) — with research suggesting a more than fivefold increased risk in patients with confirmed persistent elevation, not a single transient reading. Approximately 20–25% of patients presenting with unprovoked VTE have elevated Factor VIII without another identifiable cause.
The most common causes of high Factor VIII activity:
| Cause | Notes |
|---|---|
| Acute phase response | Factor VIII is an acute phase reactant — it rises during any acute illness, infection, surgery, or inflammation; this is the most common explanation for a single elevated reading |
| Pregnancy | Factor VIII rises progressively through pregnancy, reaching 2–3× baseline by the third trimester; this is physiological and expected |
| Estrogen-containing medications | Combined oral contraceptives, hormone replacement therapy, and estrogen patches raise Factor VIII; especially relevant in women |
| Physical stress / exercise | Strenuous exercise and acute psychological stress transiently elevate Factor VIII via epinephrine release |
| Aging | Factor VIII levels tend to rise with advancing age |
| Obesity | Independently associated with elevated Factor VIII |
| Liver disease | Paradoxically, Factor VIII may be elevated even in liver disease because endothelial cells (not just hepatocytes) produce it |
| Diabetes mellitus | Consistently associated with elevated Factor VIII in observational studies |
| Renal disease | Elevated Factor VIII observed in CKD |
| Malignancy | Various cancers — particularly carcinoma and leukemia — can elevate Factor VIII |
| Hemolytic anemias | Including sickle cell disease |
| Post-surgical state | Surgery itself triggers an acute phase response |
| After myocardial infarction or stroke | As part of the acute phase reaction |
| Desmopressin (DDAVP) | Medication used to temporarily raise Factor VIII and VWF for procedural coverage in mild hemophilia |
| Persistent unexplained elevation | When none of the above apply, persistent elevation above 150% warrants thrombophilia evaluation |
HIGH FACTOR VIII IN FEMALES — WHAT DOES IT MEAN?
This is a high-click query cluster that the existing page does not address directly.
Women have several additional causes for Factor VIII elevation beyond those shared with men:
| Situation | Factor VIII effect |
|---|---|
| Combined oral contraceptives (estrogen-containing pill) | Raises Factor VIII — one of the reasons combined OCPs increase VTE risk |
| Hormone replacement therapy (HRT) | Elevates Factor VIII, particularly oral (non-transdermal) formulations |
| Pregnancy | Progressive rise through all three trimesters; third trimester levels commonly reach 150–300% |
| Third trimester / delivery | Very high Factor VIII levels are physiological — essential to reduce hemorrhage risk at delivery |
| Postpartum period | Falls toward baseline over 4–6 weeks |
| Polycystic ovary syndrome (PCOS) | Associated with elevated Factor VIII through insulin resistance and metabolic effects |
| Menopause (without HRT) | Factor VIII generally rises slightly with aging |
In women taking the combined pill or HRT, high Factor VIII is expected and partially explains the increased VTE risk associated with these medications. If thrombophilia testing is needed, it should ideally be done off hormonal contraceptives for at least 4–6 weeks (discuss timing with a hematologist or thrombosis specialist).
WHAT DOES LOW FACTOR VIII ACTIVITY MEAN?
Low Factor VIII activity (below 50%) is clinically significant and indicates reduced clotting capacity. The lower the level, the more severe the bleeding risk.
| Low Factor VIII level | Clinical category | Bleeding pattern |
|---|---|---|
| Below 1% | Severe hemophilia A | Spontaneous bleeding into joints, muscles, and internal organs |
| 1–5% | Moderate hemophilia A | Spontaneous bleeding with minor trauma |
| 5–40% | Mild hemophilia A | Significant bleeding with surgery, dental procedures, or trauma |
| 40–50% | Sub-normal | May be clinically silent or manifest as prolonged post-surgical bleeding |
Causes of low Factor VIII:
Von Willebrand disease (VWD) is a common cause of mildly reduced Factor VIII — because VWF carries and protects Factor VIII in the circulation, reduced VWF leads to faster Factor VIII degradation and lower measured activity. Type 3 VWD (the most severe form) can reduce Factor VIII activity into the range of mild hemophilia A.
Other causes include inherited hemophilia A (X-linked, predominantly affects males), acquired hemophilia A (autoimmune Factor VIII inhibitors — rare but can occur in older adults or postpartum), liver disease (severely impaired hepatocyte function), and dilutional effects after massive transfusion.
FACTOR VIII ACTIVITY AND VON WILLEBRAND FACTOR — WHAT'S THE RELATIONSHIP?
Factor VIII and VWF (von Willebrand factor) are closely linked and frequently tested together:
| Relationship | Clinical relevance |
|---|---|
| VWF carries Factor VIII in circulation | VWF protects Factor VIII from rapid degradation |
| Low VWF → low Factor VIII | In VWD types 1 and 3, Factor VIII may be reduced secondary to low VWF |
| High VWF → high Factor VIII | Elevated VWF (an acute phase protein) contributes to elevated Factor VIII during inflammation/stress |
| Both Factor VIII and VWF are elevated in pregnancy | Both rise progressively; both are part of the physiological hemostatic preparation for delivery |
| Factor VIII:C vs Factor VIII:Ag | Activity (VIII:C) measures function; antigen measures protein quantity — discordance suggests inhibitors or qualitative defects |
Lab report note: Factor VIII activity may appear on your lab report as "Factor VIII:C" (coagulant activity) or "FVIII:C" — this is the functional assay. "Factor VIII antigen" or "FVIII:Ag" is a different test measuring protein quantity regardless of function.
MOST COMMON FACTOR VIII ACTIVITY RESULTS
| Result | Typical interpretation |
|---|---|
| Below 1% | Severe hemophilia A — major clinical finding |
| 1–5% | Moderate hemophilia A |
| 5–40% | Mild hemophilia A range — evaluate for hemophilia A or VWD |
| 50–150% | Normal |
| 150–200% | Mildly elevated — most commonly acute phase response, pregnancy, or estrogen; single readings often not significant |
| 200–300% | Significantly elevated — evaluate for persistent cause if not explained by acute illness or pregnancy |
| Above 300% | Very high — evaluate for underlying condition; acute phase response, pregnancy third trimester, desmopressin effect, or malignancy |
YOUR SPECIFIC FACTOR VIII ACTIVITY RESULT — WHAT DOES IT MEAN?
| Factor VIII result | Typical interpretation |
|---|---|
| 160% | Mildly elevated — single reading during acute illness or on estrogen is often not clinically significant; repeat when healthy |
| 170% | Mildly elevated — same context applies; common in women on combined OCP or during early pregnancy |
| 180% | Elevated — if persistent after recovery from acute illness, warrants repeat testing; thrombotic risk assessment if other risk factors present |
| 190–200% | Moderately elevated — repeat testing in 6–8 weeks recommended; evaluate for persistent cause if confirmed |
| 220% | Significantly elevated — if during pregnancy, may be physiological; if not pregnant and not acutely ill, evaluate for chronic cause |
| 250% | High — persistent elevation at this level warrants hematology evaluation, particularly if other VTE risk factors are present |
| 300%+ | Very high — evaluate for underlying cause; acute phase response, third-trimester pregnancy, desmopressin effect, or malignancy are the most common explanations in outpatients |
Key principle: A single elevated Factor VIII result is almost always less meaningful than the same value confirmed on repeat testing 6–8 weeks later, away from acute illness, surgery, or pregnancy.
HIGH FACTOR VIII AND BLOOD CLOT RISK — PUTTING IT IN CONTEXT
Factor VIII elevation does not carry the same risk in every situation. The thrombotic risk depends on the level, persistence, and co-existing factors:
| Factor VIII level | Co-existing risk factors | Thrombotic risk level |
|---|---|---|
| 150–170% | None, no prior VTE | Low — likely acute phase or lifestyle; retest and monitor |
| 180% | Combined OCP use | Moderate — estrogen + elevated Factor VIII compound VTE risk |
| 180% | Prior DVT or PE | High — prior VTE + elevated Factor VIII warrants specialist review |
| 200% | Obesity, immobility, or diabetes | Moderate-high — multiple contributing factors; assess comprehensively |
| 200%+ | OCP + obesity + prior VTE | Very high — urgent hematology evaluation |
| 250% | Persistent without obvious trigger | High — thrombophilia evaluation warranted |
| Any level | Active cancer | Context-dependent — elevated Factor VIII in malignancy is one component of a broader hypercoagulable state |
MOST COMMON FACTOR VIII CLINICAL SCENARIOS
| Pattern | Most likely explanation |
|---|---|
| Factor VIII 170–180% during or shortly after infection | Acute phase response — expected; usually returns to normal after recovery |
| Factor VIII 180–220% in second or third trimester of pregnancy | Physiological pregnancy elevation — normal; will fall postpartum |
| Factor VIII 160–180% in a woman on combined oral contraceptive | Estrogen effect — expected; consider non-estrogen alternative if VTE risk is elevated |
| Factor VIII 180% → 110% six weeks after illness | Acute phase response confirmed — no further action needed if now normal |
| Factor VIII consistently 170–200% over multiple years | Persistent elevation — constitutes a thrombophilic risk factor; hematology review appropriate |
| Factor VIII 250% with obesity and type 2 diabetes | Chronic metabolic and inflammatory elevation — addressing weight and glycemic control may help |
| Factor VIII 300%+ after desmopressin (DDAVP) injection | Expected therapeutic effect — this is how DDAVP is used in mild hemophilia A before procedures |
DOES HIGH FACTOR VIII MEAN CANCER?
This question appears in the GSC data and will grow as the page matures.
High Factor VIII does not typically indicate cancer. The most common causes of elevated Factor VIII — acute illness, pregnancy, estrogen medications, obesity, aging — are benign. However, certain cancers can cause Factor VIII elevation, and the clinical context determines whether concern is warranted:
| Pattern | Cancer concern level |
|---|---|
| Factor VIII elevated during active infection or acute illness | Very low — acute phase response is the explanation |
| Factor VIII elevated in pregnancy | Very low — physiological |
| Factor VIII elevated on estrogen medications | Very low — medication effect |
| Factor VIII mildly elevated (150–180%) with normal CBC and otherwise normal labs | Low — most common explanation is benign; retest when healthy |
| Factor VIII elevated + unexplained weight loss, fatigue, or night sweats | Moderate — evaluate for underlying malignancy |
| Factor VIII elevated + abnormal CBC (high WBC, abnormal differential) | Elevated — hematologic malignancy (leukemia, lymphoma) possible |
| Factor VIII very high (>300%) + no obvious acute trigger | Evaluate — malignancy is one cause; workup appropriate |
When cancer causes elevated Factor VIII, it is almost always accompanied by other clinical or laboratory findings. Isolated Factor VIII elevation in an otherwise healthy person with normal CBC and no symptoms is rarely the first sign of malignancy.
SHOULD I REPEAT MY FACTOR VIII TEST?
Because Factor VIII is an acute phase reactant, a single elevated reading often does not reflect a person's true baseline. The timing of the test matters enormously:
| Situation at time of testing | Recommendation |
|---|---|
| During or within 2 weeks of active infection | Repeat 6–8 weeks after full recovery |
| Within 4–6 weeks of surgery or significant trauma | Repeat after full recovery (at least 6–8 weeks post-op) |
| During pregnancy | Repeat 6–8 weeks postpartum — levels fall after delivery |
| Currently taking combined OCP or HRT | Interpret with caution; ideally retest 4–6 weeks after stopping (only if safe to do so) |
| During an inflammatory flare (RA, IBD, lupus) | Repeat during disease remission |
| No obvious trigger, single reading >150% | Repeat in 6–8 weeks to confirm persistence |
| Confirmed persistent elevation >150% on two separate tests | Consider hematology or thrombosis specialist referral |
Practical point: A Factor VIII result of 180% taken during a respiratory infection is not the same as a Factor VIII of 180% taken when you are well, three months later. Confirming persistence is essential before any clinical decision is made.
FACTOR VIII TREND INTERPRETATION
For HealthMatters users tracking Factor VIII over time:
| Pattern | Clinical meaning |
|---|---|
| 180% once during acute illness → 110% after recovery | Acute phase response confirmed — no persistent elevation |
| 170% → 180% → 190% across multiple tests over years | Persistent and rising trend — warrants hematology evaluation |
| 220% during third trimester → 120% at 8 weeks postpartum | Normal physiological pregnancy pattern |
| 160% stable across years without obvious trigger | Persistent mild elevation — constitutes a mild thrombophilic risk factor; monitor with other cardiovascular risk factors |
| 300%+ during acute illness → normalizes after recovery | Acute phase response — expected; no concern if fully resolves |
| Falling from 200% toward normal after stopping OCP | Estrogen effect confirmed — expected normalization |
WHAT IS THE FACTOR VIII ACTIVITY NORMAL RANGE?
The normal range for Factor VIII activity is 50–150% in most laboratory reference ranges. Some labs use slightly different thresholds (56–140% is another common range). Results are expressed as a percentage of "normal" activity — 100% means exactly average Factor VIII function.
Lab report decoder:
| Report label | What it means |
|---|---|
| Factor VIII Activity | Standard label — functional coagulation assay |
| Factor VIII Activity, Clotting | Same test — common Labcorp/Quest format |
| Factor VIII:C | Coagulant activity — functional test |
| FVIII:C | Abbreviated form |
| Factor VIII Activated, QN | Quantitative Factor VIII activity |
| Coag Factor VIII Activity | Same test, different lab system label |
| Factor VIII Activity Assay | Full descriptive label |
| Factor V111 Activity | Common misspelling — same test (V-I-I-I vs V-III-I) |
CAN HIGH FACTOR VIII BE TREATED?
"Treatment for high factor viii" (2 clicks, 1,906 impressions) is one of the most-searched unanswered queries on this page.
There is no direct medication to lower Factor VIII levels. Management of elevated Factor VIII is focused on reducing thrombotic risk:
| Approach | When used |
|---|---|
| Identify and treat the underlying cause | Acute phase elevation typically resolves when the trigger (infection, surgery, inflammation) resolves |
| Discontinue estrogen-containing medications | If oral contraceptives or HRT are contributing, switching to progestogen-only or non-hormonal alternatives may help |
| Anticoagulation (if VTE has occurred) | Standard anticoagulant therapy (LMWH, warfarin, or direct oral anticoagulants) is used to treat or prevent recurrent VTE in patients with elevated Factor VIII |
| Extended anticoagulation | In patients with unprovoked VTE and persistently elevated Factor VIII, extended anticoagulation may be recommended after weighing bleeding vs clotting risk |
| Lifestyle: address modifiable risk factors | Weight management (obesity elevates Factor VIII), diabetes control, smoking cessation |
| Monitoring | In patients with isolated elevated Factor VIII without VTE history, regular monitoring with attention to other thrombophilic risk factors may be appropriate |
Elevated Factor VIII alone, without other risk factors or a VTE history, does not typically require anticoagulation. The decision to treat is always individualized. Hematology or thrombosis specialist consultation is appropriate for persistent unexplained elevation above 150%, particularly in patients with personal or family history of VTE.
Seek urgent medical care if elevated Factor VIII is accompanied by any of the following — these may indicate an active blood clot:
- Leg swelling, pain, redness, or warmth (possible DVT)
- Sudden shortness of breath or rapid breathing (possible pulmonary embolism)
- Chest pain, especially when breathing deeply
- Coughing up blood
- Sudden confusion, severe headache, or one-sided weakness or numbness (possible stroke)
These symptoms require emergency evaluation regardless of Factor VIII level. Elevated Factor VIII is a risk factor for these events — the symptoms above are the reason that risk matters clinically.
FAQ about Factor VIII Activity
-
What does high Factor VIII activity mean?
High Factor VIII activity (above 150%) means the blood has elevated levels of a clotting protein, which increases the tendency toward blood clots (thrombosis) rather than bleeding. This is the opposite of hemophilia A, which involves low Factor VIII. Persistently elevated Factor VIII above 150% is associated with more than a fivefold increased risk of venous thromboembolism. The most common explanations in outpatient settings are acute illness or infection (Factor VIII is an acute phase reactant), pregnancy, estrogen-containing medications, aging, and obesity. A single elevated reading during an acute illness or inflammatory episode is less concerning than a persistent elevation over multiple tests. -
What is the normal range for Factor VIII activity?
The normal range for Factor VIII activity is 50–150% in most laboratories. Some labs use 56–140%. A result of 100% means exactly average Factor VIII function. Results below 50% fall in the hemophilia A range (with severity depending on how low). Results above 150% are elevated and associated with increased thrombotic risk, particularly when persistent. -
What causes elevated Factor VIII levels?
The most common causes of elevated Factor VIII are acute illness, infection, inflammation, or surgery (Factor VIII rises as part of the body's acute phase response), pregnancy (especially third trimester), estrogen-containing medications such as combined oral contraceptives or HRT, aging, obesity, and physical stress. Less commonly, elevated Factor VIII is associated with diabetes, renal disease, liver disease, various malignancies, and hemolytic anemias. When Factor VIII is persistently elevated above 150% without an identifiable explanation, it constitutes a recognized thrombophilic risk factor for venous thromboembolism. -
Why is Factor VIII high in females specifically?
Women have several additional reasons for elevated Factor VIII: combined oral contraceptives (estrogen raises Factor VIII — this is part of the mechanism behind the increased VTE risk with the pill), hormone replacement therapy, and pregnancy (Factor VIII rises progressively through all three trimesters, reaching 150–300% by the third trimester as part of the physiological preparation for delivery). Women with PCOS may also have elevated Factor VIII through insulin resistance. When thrombophilia testing is indicated, testing should ideally be performed off hormonal contraceptives for 4–6 weeks. -
What does low Factor VIII activity mean?
Low Factor VIII activity below 50% indicates reduced clotting capacity. This is the defining feature of hemophilia A: below 1% is severe (spontaneous joint and muscle bleeding), 1–5% is moderate, and 5–40% is mild (bleeding mainly with surgery or trauma). Von Willebrand disease is a common alternative cause of mildly reduced Factor VIII — because VWF carries Factor VIII in the blood, low VWF leads to faster Factor VIII degradation and reduced measured activity. Acquired hemophilia A (autoimmune Factor VIII inhibitors) is a rarer cause that can occur in older adults or postpartum women. -
Is elevated Factor VIII dangerous?
Persistently elevated Factor VIII (above 150%) is a recognized risk factor for venous thromboembolism (DVT and pulmonary embolism). A single elevated reading during acute illness is usually not concerning and expected to resolve. Persistent elevation in an otherwise healthy person, particularly when combined with other thrombophilic risk factors (family history of VTE, immobility, surgery, pregnancy), may warrant evaluation by a hematologist or thrombosis specialist. Elevated Factor VIII alone, without VTE history or other risk factors, does not typically require anticoagulation therapy. -
What is the difference between Factor VIII activity and Factor VIII antigen?
Factor VIII activity (Factor VIII:C) measures how well the protein functions in the coagulation cascade — a functional test. Factor VIII antigen (Factor VIII:Ag) measures how much Factor VIII protein is present, regardless of whether it functions correctly. In classic hemophilia A, both are reduced. In some qualitative defects, the antigen may be present but the activity is low. In the context of Factor VIII inhibitors (antibodies against Factor VIII), activity may be very low while antigen may be variable. Most routine clinical testing measures activity rather than antigen. -
How does Factor VIII relate to von Willebrand factor (VWF)?
Factor VIII and VWF (von Willebrand factor) circulate together in the blood — VWF acts as a carrier protein for Factor VIII, protecting it from rapid degradation. When VWF is low (as in von Willebrand disease), Factor VIII is also often reduced because it degrades faster without its carrier. When VWF is high (as in the acute phase response), Factor VIII typically rises in parallel. This is why laboratories often order Factor VIII activity alongside VWF antigen and VWF activity when evaluating for bleeding disorders.
Lab Results Explained and Tracked
What does it mean if your Factor VIII Activity result is too high?
Elevated Factor VIII activity (above 150%) means the blood has increased levels of a clotting protein, which raises the tendency to form blood clots rather than causing bleeding problems. Factor VIII is an acute phase reactant — its levels rise during any acute illness, infection, surgery, or systemic inflammation, and these transient elevations are generally not clinically significant. More concerning is persistent elevation above 150% without an obvious trigger, which constitutes a recognized thrombophilic risk factor. Research demonstrates more than a fivefold increased risk for venous thromboembolism (DVT and pulmonary embolism) in patients with persistently elevated Factor VIII. Common causes of sustained elevation include pregnancy, estrogen-containing medications (combined oral contraceptives, HRT), obesity, diabetes mellitus, chronic renal or liver disease, aging, and occasionally malignancy. There is no direct medication to lower Factor VIII; management focuses on identifying and treating underlying causes, discontinuing contributing medications where appropriate, and anticoagulation therapy in patients who develop venous thromboembolism.
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What does it mean if your Factor VIII Activity result is too low?
Low Factor VIII activity (below 50%) indicates reduced blood clotting capacity. The primary cause of inherited low Factor VIII is hemophilia A, the most common severe bleeding disorder, with severity classified by level: below 1% is severe (associated with spontaneous bleeding into joints, muscles, and internal organs), 1–5% is moderate, and 5–40% is mild (bleeding typically occurs only after significant trauma or surgery). Von Willebrand disease is another important cause of mildly reduced Factor VIII — because von Willebrand factor (VWF) carries Factor VIII in the circulation and protects it from degradation, any condition reducing VWF also lowers Factor VIII activity. Acquired hemophilia A, caused by autoimmune antibodies against Factor VIII, is a rare but serious cause of sudden-onset severe bleeding in adults without prior bleeding history, more common in older patients and postpartum women.
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