Brief Answer:
More information is needed.

Detailed Answer:
Hello and welcome,

It is highly likely the numbness and heartburn are side effects of Doxycycline.
Doxycycline most commonly causes nausea, vomiting, loss of appetite, diarrhea, photosensitivity, and also may cause numbness on the face, hands or feet (not very common).
The other causes of numbness should be excluded to diagnose the drug side effect. Therefore, I would like to know how long are you taking Doxycycline, what dose and how many times a day.
-Are you taking any other pills? Do you have any other disorders (heart disease, hepatic, renal problems)?
-What is your usual blood pressure what was the last reading?
-Do you have weakness or numbness in the extremities?
-Is the numbness on your face on one side or both?
-Can you raise both of your arms or any problem with vision or speech which occurred acutely?
-Are feeling headache or loss of balance?

The following measures may help you to decrease or even avoid Doxycycline induced nausea and vomiting: Take doxycyline with food or just after a meal with a glass of water. You should never take it on empty stomach. And after taking the doxycycline stay upright for at least 30 mins. Furthermore, you should not take the medicine before going to bed. If you are taking some other medicines (pills) better avoid taking them with doxycycline at the same time. These are the easy ways to prevent nausea or stomach discomfort from doxycycline.

Please, answer above questions so that I can guide you better. I will be happy to help you further.

Thank you.

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