The GMB and Unite are involved in the action, but West Midlands Ambulance Service (WMAS) has moved to reassure the public that crews had agreed they will still attend the most serious of incidents.
The Unite action will run from 6am to 6pm on Monday, while the GMB action will last from 6am on Monday to 8am on Tuesday.
A planned strike by GMB ambulance workers in Wales on Monday has been suspended after a pay offer from the Welsh Government, the union announced.
WMAS's emergency services operations delivery director, Nathan Hudson, said: “We have had productive discussions with our staffside colleagues to agree that ambulances will respond to – the most urgent calls such as cardiac arrests and where a crew request immediate back up at the scene of a case.
"Other very serious cases such as heart attacks, strokes, difficulty in breathing and maternity cases.
“In addition, staff in our non-emergency patient transport service will continue to convey vulnerable groups such as patients undertaking renal dialysis, cancer treatments, palliative care, emergency scans within the strike period timeframe.
“Ambulances will be dispatched where clinically appropriate.”
In a statement WMAS said: "The trust respects the right of trade union members to take such action or demonstrate their support of strike action."
It also called on the public to be aware that there may be fewer ambulances to help.
A statement said: "The industrial action means fewer ambulances on the roads and fewer staff taking your 999 calls.
"Please follow this guidance: 999 is primarily there for medical and mental health emergencies, if critically unwell or there’s a risk to life.
"Ambulance will still respond to urgent calls such as heart attacks, strokes and cardiac arrests as normal.
"If you need immediate medical care, and are unable to make your own way to hospital, please do not be afraid to call us – we will find you the right care.
"Please use 999 wisely and use the symptom checker at NHS 111 Online (www.111.nhs.uk) if you’re unsure of which service to use."