Can you get blood clots from IVIG? An In-depth Look at the Risks and Prevention

October 13, 2025 •

5 min read

According to the U.S. Food and Drug Administration (FDA), all immune globulin (IVIG and SCIG) products are required to carry a boxed warning for the risk of thrombosis, or blood clots. While considered a rare complication, it is crucial for patients and healthcare providers to understand the risk associated with IVIG therapy.

Quick Summary

Intravenous immunoglobulin (IVIG) therapy can cause blood clots, though serious thrombotic events are rare. This article discusses risk factors, potential mechanisms, signs and symptoms, and preventative strategies to mitigate the risk.

Key Points

Thrombosis Risk: The FDA requires a boxed warning on IVIG products for thrombosis (blood clots), though the risk is considered rare.
Mechanism of Action: IVIG can increase blood viscosity (thickness), leading to slower blood flow and an increased potential for clot formation.
Risk Factors: Advanced age, high dose/infusion rate, pre-existing cardiovascular disease, dehydration, and immobilization are known risk factors.
Preventative Measures: Proper hydration, a slower infusion rate, and using the minimum effective dose are crucial for reducing risk.
Recognize the Signs: Patients should be aware of symptoms such as swelling, pain in a limb, chest pain, and shortness of breath, and seek immediate medical help if they occur.
SCIG as an Alternative: Subcutaneous immunoglobulin (SCIG) is often a safer alternative for patients at high risk due to its slower, more consistent absorption.
Vigilant Monitoring: Close monitoring of patients during and after IVIG infusion is essential, especially for individuals with multiple risk factors.

The Link Between IVIG and Blood Clots

Intravenous immunoglobulin (IVIG) is a plasma-derived medicinal product containing concentrated antibodies (immunoglobulins) used to treat a variety of autoimmune, inflammatory, and immune deficiency disorders. While generally considered safe, a well-documented but rare adverse effect is the formation of blood clots, a condition known as thrombosis. This risk is significant enough that the FDA mandated a boxed warning on all immune globulin products to raise awareness among healthcare professionals and patients. Thrombotic events can manifest as deep vein thrombosis (DVT), pulmonary embolism (PE), stroke, or myocardial infarction (heart attack). Reports have shown these events can occur during or shortly after an IVIG infusion.

How IVIG Increases Thrombotic Risk

The exact mechanisms aren't fully understood, but several factors are believed to contribute to the increased risk of blood clots following IVIG administration. The primary hypothesis points to a direct effect of the large-volume infusion on the bloodstream.

Increased Blood Viscosity: The concentrated proteins within the IVIG solution can increase the thickness of the blood (viscosity). Higher viscosity leads to slower blood flow, which can promote the formation of clots, particularly in patients who are not adequately hydrated.
Platelet Activation: Some research suggests that exogenous IgG, a component of IVIG, may lead to the activation of platelets, which are critical for blood clotting.
Other Factors: Other potential mechanisms include arterial vasospasm, changes in venous compliance, and the presence of certain procoagulant factors (like Factor XIa) that may be co-purified with IgG in some manufacturing processes.

Identifying Risk Factors for IVIG-Associated Thrombosis

Certain patient-specific and procedural factors can significantly increase the risk of developing a blood clot after IVIG therapy. It's vital for healthcare providers to assess these risks before treatment to implement appropriate preventative measures.

Advanced Age: The risk of thrombosis is higher in older patients, particularly those over 60.
High Dose and Infusion Rate: Large or rapid infusions of IVIG are associated with a greater risk of adverse effects, including thrombosis.
Pre-existing Cardiovascular Risk Factors: Conditions such as hypertension, diabetes, hyperlipidemia, and coronary artery disease can heighten the risk.
History of Thrombosis: Patients with a personal or family history of blood clots are at a higher baseline risk.
Hypercoagulable Conditions: Certain underlying medical conditions that promote clotting (e.g., some hematologic cancers like CLL or MM) also increase risk.
Dehydration: Inadequate hydration before and during the infusion can increase blood viscosity.
Prolonged Immobilization: Extended periods of immobility, such as after surgery or in hospitalized patients, are a classic risk factor for DVT.
Central Vascular Catheters: The presence of an indwelling catheter can create a localized risk for clot formation.

Recognizing the Signs and Symptoms of a Blood Clot

Prompt recognition of the signs and symptoms of thrombosis is critical for effective treatment. While symptoms can vary depending on the location of the clot, it is important to be vigilant for any of the following during or after an IVIG infusion:

Deep Vein Thrombosis (DVT): Swelling, pain, redness, or warmth in an arm or leg, often localized to the calf or thigh.
Pulmonary Embolism (PE): Sudden chest pain, shortness of breath, pain with breathing, and a rapid heartbeat.
Stroke: Sudden numbness or weakness of the face, arm, or leg (especially on one side), confusion, trouble speaking or understanding, vision problems, and dizziness.
Myocardial Infarction (MI): Chest pain or pressure, discomfort spreading to the arm, back, neck, jaw, or stomach, and shortness of breath.

A Comparison of IVIG and SCIG Thrombosis Risk

Subcutaneous immunoglobulin (SCIG) is an alternative administration method that involves infusing immunoglobulin under the skin. The risk profile differs from IVIG, offering potential advantages in specific patient populations.


Feature	Intravenous Immunoglobulin (IVIG)	Subcutaneous Immunoglobulin (SCIG)
Mechanism	Infusion into a vein, leading to rapid increase in serum immunoglobulin levels.	Infusion under the skin, resulting in slower, more consistent absorption.
Infusion Volume	Large volume of fluid infused over several hours to days.	Smaller volumes infused more frequently (e.g., daily or weekly).
Hyperviscosity Risk	Higher risk due to large, concentrated volume causing a significant, acute increase in blood viscosity.	Much lower risk as the total volume is smaller and absorbed gradually, avoiding sharp viscosity changes.
Peak Concentration	High, rapid peak concentration of immunoglobulin in the blood.	Lower, more stable peak concentration due to slower absorption.
Risk Profile	Elevated risk of thrombotic events, especially with high dose/rate and pre-existing risk factors.	Generally considered a lower risk for thrombosis compared to IVIG due to slow absorption and lower peak concentration.

Strategies for Minimizing Risk

Preventing IVIG-related thrombosis is a priority for safe patient care. Healthcare providers employ several strategies to mitigate the risk.

Ensure Adequate Hydration: Patients should be well-hydrated before, during, and after the infusion to prevent an increase in blood viscosity.
Slow Infusion Rate: For at-risk patients, administering the IVIG at the minimum concentration available and slowest practicable infusion rate can reduce the risk of acute hyperviscosity. The rate is often started low and increased gradually, especially during the first infusion.
Careful Dosing: Using the minimum effective dose of IVIG is recommended, as higher doses are associated with an increased risk.
Consider SCIG: In patients with a high risk of thrombosis, such as those with a history of blood clots or significant cardiovascular disease, switching to subcutaneous immunoglobulin (SCIG) may be a safer alternative.
Pre-medication and Monitoring: While evidence is mixed, some protocols include pre-medication and close monitoring during the infusion. For high-risk individuals, anticoagulant or antiplatelet therapy may be considered, though its overall efficacy in preventing IVIG-related clots is still debated.

The Importance of Vigilant Monitoring

Both the patient and the healthcare team play a crucial role in preventing and managing IVIG-related thrombotic events. Patients receiving IVIG should be educated on the potential risks and the signs of a blood clot. Healthcare providers must conduct a thorough risk assessment, monitor the patient's fluid status and vital signs throughout the infusion, and remain vigilant for any warning signs in the hours and days following the treatment.

For patients with pre-existing risk factors, or those showing any signs of a potential clot, the infusion should be adjusted or stopped, and appropriate medical evaluation should be performed immediately. While the risk of a blood clot from IVIG is low, the potential for serious consequences makes a proactive and cautious approach essential for ensuring patient safety.

Conclusion

In summary, while the risk is rare, you can get blood clots from IVIG therapy, as indicated by the FDA's boxed warning. The primary mechanism is thought to be an increase in blood viscosity, though other factors like platelet activation also play a role. Key risk factors include advanced age, high infusion dose and rate, dehydration, and pre-existing cardiovascular conditions. By ensuring proper hydration, using a slow and steady infusion rate, and remaining vigilant for symptoms like swelling, pain, or chest discomfort, patients and providers can significantly minimize this serious, though uncommon, complication.

For additional information, you can consult sources like the National Institutes of Health.

Frequently Asked Questions

Yes, it is possible to get a blood clot from IVIG, although it is considered a rare but serious side effect. The FDA requires a boxed warning on all IVIG products about the risk of thrombosis.

IVIG infusion can cause blood viscosity (thickness) to increase, which can lead to blood clots. Other contributing factors include platelet activation, vasospasm, and potentially procoagulant factors in the product.

Thrombotic events can occur during the infusion or within days to several weeks afterward. However, some studies indicate the risk for arterial clots like stroke or heart attack is highest within the first 24-48 hours.

Key risk factors include advanced age, high infusion dose and rate, dehydration, prolonged immobilization, and pre-existing conditions like heart disease, diabetes, or a history of prior blood clots.

Preventative measures include ensuring adequate hydration before and during the infusion, administering the IVIG at a slow, minimum practicable rate, and carefully assessing patient risk factors beforehand.

Case reports have suggested that arterial thrombotic events, such as stroke and myocardial infarction, may be more common, particularly shortly after the infusion. However, venous clots like DVT and PE are also a risk.

You should seek immediate medical attention by contacting your doctor or calling emergency services. Symptoms like sudden chest pain, shortness of breath, unexplained swelling or pain in a limb, or sudden numbness or weakness require prompt evaluation.