What is your age ?
Any other medical problems?
Have you been in situation of prolonged rest lately ? ( long car ride or plane trip as example? )
Any recent surgery that you are in recovery ?
The history of sudden swelling and pain of ONE calf to foot concerns me that you may have a clot in this leg as a possible cause..
This is known as a DVT if this is your cause..
If you should have a DVT ( = deep vein thrombosis ) then you should go immediately to the ER and be checked..
They do a blood test >> D-dimer which looks for abnormal clotting and to check and ultrasound of the leg
So I urge you to to go to the ER ...
I hope that this information is helpful for you.
Let me know if you have further questions or concerns.
I will be happy to get back with you.
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Thank you and Best Regards,