Specialty Testing Guide › TruHealth Micronutrient Testing
What you eat and what your body absorbs are two different things. Celiac disease, low stomach acid, common medicines such as acid blockers and metformin, inflammatory bowel disease and weight-loss surgery can all lower your nutrient levels even when your diet looks fine on paper.
When a deficiency keeps coming back, or several nutrients are low at once, the gut is often where the answer lies. In those cases, finding and treating the absorption problem matters more than adding another supplement.
Key takeaways
- Each part of the gut handles different nutrients, so the location of a problem shapes which levels fall.
- Unexplained low iron is a common clue to celiac disease, which is diagnosed with blood antibodies and usually a biopsy while still eating gluten.
- Long-term acid blockers are linked to lower B12 and lower magnesium.
- Weight-loss surgery patients need lifelong monitoring, since deficiencies are common before and after the operation.
How the gut absorbs nutrients
Absorption is a relay, and each part of the gut has a job:
- Stomach. Acid frees B12 from food and helps iron dissolve. The stomach also makes intrinsic factor, the protein B12 needs to be absorbed later.
- Upper small intestine. The main site for iron, calcium and folate absorption.
- Pancreas and gallbladder. Enzymes and bile break down fat so that vitamins A, D, E and K can be absorbed.
- Lower small intestine. Where B12 and bile acids are taken back into the body.
A problem at any step lowers the nutrients that depend on it. That is why the pattern of low results can point a clinician toward the part of the gut involved.
Celiac disease
Celiac disease is an immune reaction to gluten that damages the lining of the small intestine. It often shows up as something other than gut symptoms, such as iron deficiency, low bone density, fatigue or abnormal liver tests. Guidelines describe it as a condition that behaves more like a whole-body disorder than an isolated gut disease.1
Testing starts with a blood antibody test, usually tissue transglutaminase IgA with a total IgA level, and in adults most diagnoses are confirmed with an intestinal biopsy.1 Both depend on you still eating gluten. If you cut gluten first, the tests can come back falsely normal, which is why our guide on not going gluten-free before testing matters.
Iron is the classic clue. Experts advise that celiac screening be considered routinely in people with iron deficiency.2
Low stomach acid and common medicines
Stomach acid falls with age, with a long-standing H. pylori infection and with autoimmune gastritis. Medicines that reduce acid have a similar effect. In a large Northern California study, two or more years of proton pump inhibitors or H2 blockers was linked with a higher risk of B12 deficiency.3 A pooled analysis of observational studies also linked proton pump inhibitor use to low blood magnesium.4
Metformin, a widely used diabetes medicine, can lower B12 over years as well.5 None of this means you should stop a medicine on your own. It means long-term users should ask whether periodic B12 or magnesium checks make sense.
Weight-loss surgery and other gut conditions
Bariatric surgery changes how food moves through the gut, and some procedures bypass the very sections that absorb iron, calcium and B12. Professional guidelines note that many people already have at least one vitamin or mineral deficiency before surgery, and that lifelong supplements and regular blood tests are part of standard care afterward.6
Other conditions that reduce absorption include Crohn's disease, especially when it affects the lower small intestine, chronic pancreatitis or other causes of low pancreatic enzymes, past bowel surgery and long-lasting diarrhea from any cause. Signs that absorption may be the problem include pale, greasy or floating stools, unplanned weight loss and several deficiencies at the same time.
Where specialty gut and nutrient tests fit
Standard tests come first for absorption problems: nutrient blood levels, celiac antibodies and, when needed, a gastroenterology evaluation. Specialty tests answer narrower questions, and it helps to know what each does not do.
- A stool panel such as the GI-MAP looks at microbes and some digestive markers. It does not measure how well you absorb nutrients and does not diagnose celiac disease. See the GI-MAP testing hub.
- A wheat-reactivity panel such as the Wheat Zoomer reports antibodies to wheat proteins, but it does not replace the guideline path for diagnosing celiac disease. See the Wheat Zoomer testing hub.
- TruHealth from TruDiagnostic estimates nutrient-related markers from DNA methylation patterns rather than measuring blood levels directly. A low estimate is a reason to check with a standard blood test, not proof of malabsorption.
Here in the Philadelphia area, as anywhere, alarm signs such as bleeding, weight loss, trouble swallowing, or new iron deficiency in a man or a woman past menopause, call for a medical workup, often with a gastroenterologist, before any specialty panel.
Your next step
If you want to compare a methylation-based nutrient estimate with direct blood measurements, read how this test compares with blood micronutrient tests. The micronutrient testing hub gathers the full series.
Frequently asked questions
Can probiotics fix poor absorption?
There is no good evidence that probiotics correct the main causes of malabsorption, such as celiac disease, low stomach acid or surgery. Finding and treating the underlying cause is the reliable path.
Should I take higher doses of supplements if I absorb poorly?
Sometimes, but only with a clinician. Some deficiencies, such as B12 after certain surgeries or in pernicious anemia, may need injections or specific forms, and doses should follow your blood results.
Does leaky gut cause nutrient deficiencies?
Increased intestinal permeability is a real research topic, but there is no validated clinical test for it and no proof it causes deficiencies on its own. Established causes like celiac disease and medicines are far more likely explanations.
Related reading
This article is for general education and is not medical advice. Decisions about testing and treatment should be made with your clinician. If you have severe symptoms, call 911. For a suspected poisoning, call Poison Control at 1-800-222-1222.
