Get emergency medical help if you have signs of an allergic reaction to diltiazem: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
Call your doctor at once if you have:
slow heartbeats;
pounding heartbeats or fluttering in your chest;
a light-headed feeling, like you might pass out;
shortness of breath (even with mild activity), swelling, rapid weight gain;
nausea, upper stomach pain, itching, tired feeling, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes); or
severe skin reaction - fever, sore throat, swelling in your face or tongue, burning in your eyes, skin pain followed by a red or purple skin rash that spreads (especially in the face or upper body) and causes blistering and peeling.
Common diltiazem side effects may include:
swelling;
dizziness, weakness;
headache;
nausea; or
rash.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
 Diltiazem side effects (more detail)
