Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Call emergency services immediately if the person:
Call emergency services rather than a poison centre when there is severe breathing trouble, collapse, or another immediately life-threatening symptom.
This is different from emergency care and can usually be discussed at a planned appointment.
And for anyone, someone who:
Urgent medical assessment is also needed for repeated vomiting, a very swollen abdomen, inability to pass stool or gas, blood in vomit or stool, or persistent coughing after choking.
Contact a poison centre promptly after someone swallows laundry starch, spray starch, craft starch, an industrial product, or a product with unknown ingredients.
Call even if symptoms have not started.
A poison specialist can use the label and amount to advise whether home observation is appropriate.
Arrange routine follow-up if abdominal symptoms do not settle, breathing symptoms continue after an exposure, or you repeatedly crave and eat uncooked starch.
The article also says
In the United States, Poison Help is available at 1-800-222-1222.
Elsewhere, contact your local poison information service.
Every sign above is quoted from the sofidex article on Starch poisoning. If you are not sure, err upward — it is always reasonable to be checked.