Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Seek emergency care for:
These symptoms have several possible causes and do not prove that worms are responsible.
Contact a healthcare service promptly if you have blood in your bowel movements, black stools, worsening weakness, fever with abdominal symptoms, or persistent vomiting.
Tell a healthcare professional promptly about possible past Strongyloides exposure if you are due to start corticosteroids, chemotherapy, transplant medicines, or other treatment that suppresses immune defences.
Arrange a routine medical appointment if you see a worm or repeated worm-like segments in a bowel movement, have persistent anal itching, or develop ongoing abdominal symptoms after travel or possible exposure.
Also seek advice for unexplained anaemia, weight loss, or symptoms that return after treatment.
The article also says
Get medical advice before taking worm treatment if you are pregnant, breastfeeding, treating a young child, taking several medicines, or have liver disease.
Product suitability differs by medicine and location.
Every sign above is quoted from the sofidex article on Worms in humans. If you are not sure, err upward — it is always reasonable to be checked.