Check Costco's store brand.

Yes, get serum antibody testing done for celiac disease. You could also have NCGS (Non Celiac Gluten Sensitivity). NCGS shares many of the same symptoms of celiac disease but does not damage the lining of the small bowel as does celiac disease. There is no test for it. A diagnosis for NCGS depends on first ruling out celiac disease. It is 10x more common than celiac disease. Some experts feel it can be a precursor to the development of celiac disease. Eliminating gluten from your life is the antidote for both.

Biopsy results can be negative despite positive serum antibody results for these reasons: 1. Early onset of celiac disease. Inflammation has been happening for long enough to cause damage to the small bowel lining that is observable in the biopsy sample. 2. The damage is in the part of the small bowel lining below the duodenum. The duodenum is the part of the small bowel immediately below the outlet of the stomach. 3. The damage is patchy and was missed by the one doing the biopsy. A thorough biopsy would include several samples taken from different areas of the duodenum. Not all scoping is done this thoroughly, unfortunately. 4. The positive serum antibody results are caused by some other medical problem, food or medication that mimics the inflammatory reaction typical of celiac disease.

I am not a cigarette smoker and the only time I ever tried to smoke a cigarette was when I was 13 years old and it made me nauseous. I'm sure if I were to have kept at it, I would have developed a tolerance to nicotine such that it would no longer have made me nauseous. But I also imagine that if I quit for a good amount of time and went back to it I would be made nauseous at first again until I built up a tolerance to it. I could site many examples of toxic things we could put into our bodies in small doses at first and build up a tolerance to them but lose it again after quitting them. That's how gluten can work for the celiac. When we force our bodies to deal with it by consuming it every day, the body does the best it can to handle it and sort of gets by, even though it may be doing long term damage. But if we quit and remain off for a good period of time, we lose that tolerance. Yes, for the celiac, gluten ingestion causes the immune system to mount an attack in the lining of the small bowel. By definition, that is celiac disease. But we now know that in addition to damaging the small bowel lining, gluten can also cause inflammatory reactions in other organ systems such as the liver. About 20% of celiacs have elevated liver enzymes. So, the effects of gluten ingestion for the celiac can by somewhat system in some cases. Another example is headaches. Migraine rates are higher for the celiac population than for the general population.  Small amounts of gluten ingestion would likely cause less inflammation than larger amounts. The absence of a discernable reaction after gluten ingestion does not necessarily equate to no inflammation. This factoid can make it more challenging for "silent" celiacs to get a handle on cross contamination. It takes weeks of consistent gluten consumption for antibody levels to build up to detectable levels in the blood. Occasional accidents and missteps are not likely to be reflected in serum antibody testing. After beginning the gluten free diet, antibody levels begin to drop but it can take weeks or months to return to normal (negative) levels. For adults, it can take two years or more for complete healing of the small bowel lining but for children and young people it can be much shorter. Follow-up testing, either serum antibody or endoscopy/biopsy can gauge healing progress and can also shed light on the success and consistency of eliminating gluten from the diet. 

Hello, I'd have been here sooner, but I got tangled up in yarn... Restless leg syndrome (RLS) I've had. It's often associated with iron deficiency and B12 deficiency, but can also show up with any deficiencies in Vitamin C, copper, Vitamin D, and Thiamine, Pyridoxine, and magnesium.  B12, Thiamine, and Pyridoxine will also help with peripheral neuropathy, that burning sensation.   (See... https://pmc.ncbi.nlm.nih.gov/articles/PMC9804944/ ) Long Covid can be the result of nutritional deficiencies, as well.  Zinc, Selenium, Vitamin D, B12, Thiamine, Riboflavin, Pyridoxine, Niacin, and Choline.  (See... https://pmc.ncbi.nlm.nih.gov/articles/PMC10015545/  and https://pubmed.ncbi.nlm.nih.gov/36587225/ ) I agree with @Wheatwacked to get Vitamin D level higher, 80 ng/ml.  Taking high doses of Vitamin D to correct a deficiency has been found to be beneficial.  I took Vitamin D3 supplements throughout the day when I had a severe deficiency.  It got my level up quickly and I started feeling much better.   (See... https://pubmed.ncbi.nlm.nih.gov/28167237/ , https://pmc.ncbi.nlm.nih.gov/articles/PMC4824637/) Vitamin D is a fat soluble vitamin.  Fats can be difficult to digest and absorb, so most of the newly diagnosed can be low in the four fat soluble vitamins (A,D,E,K).  A deficiency in Vitamin A can cause dry eyes.  Omega Threes and Evening Primrose Oil help with dry eyes, too.  (https://pmc.ncbi.nlm.nih.gov/articles/PMC10363387/) Blood tests are not accurate measurements of vitamin levels.  Blood tests will reflect any supplements being taken.  Blood tests do not measure how much of a vitamin is stored inside cells.  Supplementing with all eight essential B vitamins for several months will boost your ability to absorb the needed nutrients. A deficiency in Cobalamine, B12, can be aggravated by anesthesia.  Cobalt in Cobalamine binds irrevocably, irreversibly with the Nitrogen in anesthesia, rendering B12 useless.  Supplementing with B12 after exposure to anesthesia is beneficial.  (https://pubmed.ncbi.nlm.nih.gov/8250714/) Pyridoxine B6 and Riboflavin B2 as well as B12 are needed to lower histamine levels (produced during the inflammation process that occurs in Celiac Disease). This can help relieve the sinus pressure.  Riboflavin B2 and Thiamine B1 are helpful with headaches.   We need more Thiamine when we are emotionally stressed, physically ill, and physically active.  Benfotiamine, a form of Thiamine, has been shown to promote intestinal healing.  Thiamine is helpful in relieving anxiety.   (https://pmc.ncbi.nlm.nih.gov/articles/PMC10682628/  , https://pmc.ncbi.nlm.nih.gov/articles/PMC8451766/ ) Celiac Disease causes malabsorption of vitamins and minerals.  It is rare to have a single vitamin deficiency.  Malabsorption in celiac disease affects all the nutrients we need.  Some vitamins just run out sooner than others because they can't be stored or we have a metabolic need for more.  (https://pmc.ncbi.nlm.nih.gov/articles/PMC10106602/ ) Hope this helps!