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 for breathing difficulty, collapse, seizure, inability to wake, or severe chest symptoms.
And for anyone, someone who:
Seek urgent reassessment for worsening vomiting, marked weakness, confusion, fainting, reduced urination, or new palpitations.
Follow-up depends on the severity of the exposure.
A poison center may recommend home observation for a low-risk exposure, while a clinician may arrange repeat blood tests after significant symptoms, abnormal laboratory results, or kidney injury.
Routine follow-up may include checking calcium, magnesium, kidney function, and other electrolytes.
A clinician may also review every prescription medicine, over-the-counter product, vitamin, and supplement to identify overlapping ingredients.
And for anyone, someone who:
The article also says
Ongoing heartburn should not be managed by repeatedly exceeding an antacid label.
Frequent symptoms may need a separate evaluation to look for acid reflux, an ulcer, medication effects, or another cause.
A clinician or pharmacist can help select a safer long-term plan based on the person’s health and other medicines.
Store antacids and supplements out of children’s sight and reach.
Keep products in their original containers so the ingredients and strength remain available if an exposure occurs.
Every sign above is quoted from the sofidex article on Calcium carbonate with magnesium overdose. If you are not sure, err upward — it is always reasonable to be checked.