Aspirin is a commonly used medication for pain relief, fever reduction, and anti-inflammatory purposes. However, it is important to note that aspirin can cause stomach bleeding as a side effect. According to the FDA, aspirin-containing antacid medicines can cause bleeding [2]. Additionally, a study published in the National Library of Medicine found that aspirin use can increase the risk of gastrointestinal bleeding [3]. It is recommended that individuals who are at a higher risk of bleeding, such as those with a history of stomach ulcers or bleeding disorders, should avoid taking aspirin or use it with caution and under the supervision of a healthcare provider [3]. Patients who experience symptoms of stomach bleeding, such as black or bloody stools, abdominal pain, or vomiting blood, should seek immediate medical attention [2]. It is important to follow the recommended dosage and usage instructions when taking aspirin and to consult with a healthcare provider if there are any concerns about its potential side effects [1].

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/ASPIRIN
[2] https://www.fda.gov/consumers/consumer-updates/warning-aspirin-containing-antacid-medicines-can-cause-bleeding
[3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3086018/