I had the 4 Pfizer shots with the same symptoms after each: strong fatigue, muscle aches, breathing difficulties and brain fog. They would last for 3-4 days and I would get better. About a week after the 4th shot, I went on a nature hike with my granddaughter and the next day all the symptoms returned. That was my first PEM and they continued for 1.5 years in a “roller coaster” fashion and I could not plan on doing any family events because I was afraid of “taking a dive” at any time. I never tested positive for Covid and all my annual “wellness” blood tests came out normal, as in pre-pandemic.
Early this year, I saw a study that was done in Italy on using L-Arginine and vitamin C that reduced the Long Covid symptoms. L-Arginine creates nitric oxide that we need to convey oxygen to our tissues. I started taking a low dose and found that the PEM was gone. That encouraged me.
I added L-Citrulline that turns into L-Arginine. I limited the vitamin C to 500mg per day to avoid stomach discomfort that I experienced at 1000 mg per day. My symptoms have drastically reduced. I have added L-Carnitine and Creatine.
Nitric oxide is needed for circulating oxygen to our tissues. It relaxes the blood vessels that allows for better flow of the blood to carry the oxygen. It lowers blood pressure.
However, the production of nitric oxide in our bodies can be reduced by a diet in high salt, high fat or high sugar. It can even be lowered with using a mouth wash that destroys the good bacteria in our mouth. The production system for nitric oxide is very sensitive to what else enters our body.
My theory is that the Covid vaccines impacted our ability to produce nitric oxide which is causing our symptoms. Low oxygen levels in our tissue can cause fatigue, muscle aches, breathing problems and brain fog. I believe that my “roller coaster” symptoms were dependent on the level of nitric oxide producing foods that I consumed, such as beets, celery, cocoa and citrus (vitamin C) that improved my symptoms. They are now my dietary focus. But when I did not have them in sufficient quantity, I “took a dive”.

Below is an excerpt from an article on the study in Italy that showed “chronic fatigue of the post-Covid syndrome is precisely associated with an alteration in the metabolism of arginine” and that “in patients with long Covid there is an alteration of the metabolism of arginine, which stimulates nitric oxide, a key enzyme for proper immune and vascular function.”
The mechanism that leads to chronic fatigue in Long Covid patients has been discovered, according to new Italian research.
“The mechanism of action that leads to the state of fatigue, or disabling exhaustion, linked to Long Covid which affects 1 in 3 people who are victims of the Sars-CoV-2 infection has been discovered: it is triggered by a deficit of arginine, an amino acid naturally produced by the body.
This is demonstrated by a study on long Covid conducted by the Agostino Gemelli IRCCS University Polyclinic Foundation – Catholic University Campus of Rome, according to which the chronic fatigue of the post-Covid syndrome is precisely associated with an alteration in the metabolism of arginine.
The new study highlighted that in patients with long Covid there is an alteration of the metabolism of arginine, which stimulates nitric oxide, a key enzyme for proper immune and vascular function.
The researchers also demonstrated that the administration of 1.6 grams of arginine and 500 mg of liposomal vitamin C for 28 days restores the metabolism of arginine to a normal level and effectively counteracts fatigue.”
https://www.coronaheadsup.com/health/long-covid/long-covid-fatigue-caused-by-an-arginine-deficiency/
If you are on any meds, review them for interactions with L-Arginine supplements, or talk to your doctor.