What are the side effects of Alteplase Injection?
Last updated September 7, 2026.
**Bleeding is the main side effect of alteplase, ranging from bruising at the IV site to bleeding inside the brain, stomach, or urinary tract.** Alteplase works by breaking down clots, so anything that was already fragile can bleed more easily. Common milder effects include oozing at the injection or catheter site, nosebleeds, bleeding gums, nausea, vomiting, fever, and a drop in blood pressure. Less often, people have an allergic reaction with swelling of the lips, tongue, or throat, and some develop irregular heartbeats when blood flow returns to the heart. Because alteplase is given in a hospital or infusion setting, your team checks your blood pressure and neurologic status often during and after the dose. Tell them right away about a sudden severe headache, new weakness or trouble speaking, black or bloody stools, pink or red urine, or coughing up blood.
What to do
- Speak up fast: Tell staff right away about a sudden severe headache, new numbness or weakness, vision change, or trouble speaking.
- Watch for hidden bleeding: Black or tarry stools, pink or red urine, coughing up blood, or vomit that looks like coffee grounds all need immediate attention.
- Share your full med list: Blood thinners, aspirin, and other antiplatelet drugs raise bleeding risk, so your team needs to know everything you take.
- Mention recent events: Recent surgery, a head injury, a stroke, a biopsy, or uncontrolled high blood pressure change how alteplase is used.
- Expect close monitoring: Frequent blood pressure and neurologic checks are routine after a dose, and limiting needle sticks helps reduce bruising.
- Ask before you leave: Get clear instructions on how long to avoid injections, shaving with a razor, and contact sports or falls.
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