heart palpitations/ palpitations; patient decided on her own to take Levoxyl sublingually / started taking a little more/ started increasing the thyroid medication; This is a spontaneous report from a contactable consumer (patient) received via the Medical Information Team and the Pfizer-sponsored Program.   A 74-year-old female patient received the first dose of BNT162B2 (PFIZER-BIONTECH COVID-19 VACCINE; lot/ batch number: EL1283 and expiry date unknown), via an unspecified route of administration on 20Jan2021 (at 74 years old) at a SINGLE DOSE for COVID-19 immunization, "for fun, for fear";  and levothyroxine sodium (LEVOXYL Tablet), orally from 12Nov2020 to an unspecified date and sublingually at the beginning of Jan2021 (also reported as 20Jan2021) to an unspecified date at 0.25 mg, daily (she would take half of the tablet in the morning and half at night) for hypothyroidism. The patient's medical history included hypothryroidism from an unknown date. Patient's height used to be five foot three with weight: between 140 to 150 pounds, usually around 145 pounds. Concomitant medications included Magnesium Malate at 1000mg and at 200mg (lot number: X002OISTE1 and expiration date: Aug2023). She got Magnesium the heart doctor told her to get. She stopped taking it on 22Jan2021, two days after the first episode on the 20Jan2021. Patient previously had problems with another thyroid drug, it was a natural thyroid medication called NP THYROID and she had palpitations on that one. The drug was not as standardized because it is natural thyroid. She started it in 2019 and took for a year and half. She was on a higher dose, 30mg originally and dropped down to 15mg or .25gram because it was "too much." The pharmacy sent a notice out that a dosage was too high in May or Jun. Then in Sep the dosage was too low. She asked pharmacy about the lot number and they said they didn't put it on there. She got it from (Pharmacy name withheld). RX number: 1677890-07298. Manufacturer: (Company name withheld). The dose amount had dropped, and she wasn't getting enough of the drug and her TSH had gone very high. That was causing the palpitations. Then she was switched to levothyroxine sodium.  On 20Jan2021, patient experienced heart palpitations. It was reported that at the beginning of Jan2021 (also reported as 20Jan2021), patient decided on her own to take levothyroxine sodium sublingually and she experienced heart palpitations. Patient confirmed that this was not prescribed to be taken sublingually. Patient asked if taking levothyroxine sodium sublingually increase its potency. Also, on 20Jan2021, she received the first dose of the Pfizer Covid vaccine. Her thyroid levels taken this past Friday (29Jan2021) were normal. Patient asked if taking the Covid vaccine with levothyroxine sodium cause palpitations. She wanted to know if there is data on taking levothyroxine sodium sublingually. She wanted to know if it has more of an effect and wondered if taking levothyroxine sodium sublingually might have effected it. She doubts if Pfizer has studied it sublingually, but would that have increased the potency of the levothyroxine sodium? Maybe she got more than she was getting before. On 20Jan2021 she received Pfizer's COVID19 Vaccine. She started having palpitations that night and she was not sure if the vaccine had anything to do with it. The palpitations are ongoing. Some days they get worse and other days they are ok. She thought she was low on levothyroxine sodium, so she started taking a little more. She knew she was supposed to call the doctor.  The day after she got palpitations, she started increasing the thyroid medication and it didn't seem to help. Over- the- counter Zinc, Magnesium, and Potassium helped. Zinc seemed to have most effect at trying to reduce them. It was reported that patient took Zinc 30 Orotate (lot number: 210606, expiration date: Nov2020). She took it on three occasions when she had it bad. Within a few hours after she took it the palpitations calmed down. Patient also took Potassium (lot number: 8BO3217 and expiration: Mar2003). She has only taken it twice since the palpitations.  She doesn't take those normally except for the Magnesium. She went to the doctor yesterday, but she didn't see the doctor and only saw the nurse. She underwent thyroid test on Friday, 29Jan2021 and it was within range. The TSH was not high, meaning she was getting the correct amount. She doesn't know how quickly taking the half thyroid pill would have effected it at that point. Supposedly she is within range, but still was having palpitations. Some days are really bad and other days not so bad. The levothyroxine sodium is the same prescription bottle. She just switched from taking it orally to sublingual. She took it orally for the first several months and then switched to sublingual, for both, she would take half of the tablet in the morning and half at night because she was so reactive to medication. She was concerned if she should get the second dose of COVID-19 vaccine because "you never know." The patient further reported that she saw the cardiologist in the fall, and he did EKG and didn't find anything unusual. She is going to go see him again tomorrow because her other doctor said if the heart palpitations are bad enough, she needs to go to the ER and get EKG. She just had EKG in the fall. She knows it was a reaction to something. As soon as she started getting more thyroid medication in her, it went away. The action taken in response to the event for levothyroxine sodium was unknown and for BNT162B2 was not applicable.  Outcome of the event heart palpitations/ palpitations was not recovered.