Yeast F45 IgG
It measures IgG antibodies to yeast (F45) to help contextualize symptoms and diet trials, with easy ordering and Quest-based labs via Vitals Vault.
This panel bundles multiple biomarker tests in one order—your report explains how results fit together.
A Yeast F45 IgG test measures your immune system’s IgG antibodies to yeast. In most lab catalogs, “yeast” here refers to baker’s/brewer’s yeast (Saccharomyces) used in foods and fermentation.
This is not the same as an allergy test. IgG results are sometimes used to guide a structured elimination-and-rechallenge plan when you and your clinician are trying to understand whether certain foods are contributing to symptoms.
Because IgG can reflect exposure as well as immune recognition, your result is most useful when it is interpreted alongside your diet history, timing of symptoms, and other testing that rules out conditions that look similar.
Do I need a Yeast F45 IgG test?
You might consider Yeast F45 IgG testing if you notice symptoms that seem to track with yeast-containing or fermented foods and you want a more organized way to plan a diet trial. People commonly look into this when they have recurring bloating, changes in bowel habits, headaches, skin flares, or “brain fog” that do not have a clear trigger.
This test can also be reasonable if you have already tried broad dietary changes and want to narrow the focus. For example, if you tolerate many foods but consistently feel worse after beer, wine, breads, or other yeast/fermented products, an IgG result may help you decide whether a targeted elimination is worth doing.
You may not need this test if you are concerned about immediate allergic reactions such as hives, swelling, wheezing, or anaphylaxis after eating. Those scenarios are better evaluated with IgE testing and clinician-directed allergy care.
No single IgG result diagnoses “yeast intolerance,” Candida overgrowth, or a specific gastrointestinal disease. Testing is most helpful when it supports a clinician-guided plan that includes symptom tracking and a clear retest or reintroduction strategy.
This is a laboratory-developed test performed in a CLIA-certified lab; results are for risk/response assessment and should be interpreted with your clinician, not used as a standalone diagnosis.
Lab testing
Order Yeast F45 IgG through Vitals Vault and schedule your blood draw.
Schedule online, results typically within about a week
Clear reporting and optional clinician context
HSA/FSA eligible where applicable
Get this test with Vitals Vault
Vitals Vault lets you order Yeast F45 IgG testing without a separate doctor visit, and then complete your blood draw through a national lab network.
After your results post, you can use PocketMD to translate the number into next steps that fit your situation, such as how long to run an elimination trial, what counts as a meaningful change, and what companion labs to consider if symptoms persist.
If you are already working with a clinician, you can bring your report to that visit and use it as one more data point. If you are not, PocketMD can help you prepare questions and decide whether follow-up testing or a broader panel makes sense before you retest.
- Order online and schedule a local blood draw
- Results you can download and share with your clinician
- PocketMD guidance for interpretation and follow-up planning
Key benefits of Yeast F45 IgG testing
- Helps you evaluate whether yeast-containing foods are a plausible target for a structured elimination-and-rechallenge trial.
- Adds objective context when symptoms are delayed, inconsistent, or hard to connect to a single meal.
- Can support more focused diet changes instead of broad, restrictive “cut everything” approaches.
- Provides a baseline you can compare against if you retest after a sustained dietary change.
- May help differentiate “food trigger” questions from true immediate allergy concerns that require IgE testing.
- Pairs well with symptom logs and gut-focused evaluation when you are trying to sort out overlapping causes.
- Gives you a clear result you can review with PocketMD and your clinician to plan next steps.
What is Yeast F45 IgG?
Yeast F45 IgG is a blood test that measures immunoglobulin G (IgG) antibodies directed against yeast proteins. “F45” is a lab code used to identify the yeast antigen being tested.
IgG antibodies are part of your immune system’s memory and exposure response. Unlike IgE (the antibody class involved in classic immediate allergies), IgG responses are not a reliable marker of anaphylaxis risk. Instead, IgG is sometimes used in the context of food sensitivity discussions, where symptoms may be delayed by hours to a day and may involve the gut, skin, or general well-being.
A key limitation is that IgG can rise simply because you eat a food often. That means a higher result does not automatically mean the food is “bad” for you. The practical value comes from combining the result with your history: what you eat, how often, what symptoms you get, and whether symptoms improve and return with a careful elimination and reintroduction plan.
What counts as “yeast” in everyday life?
In food contexts, yeast commonly refers to baker’s or brewer’s yeast used in bread, beer, and many fermented products. Some people also react to foods that contain yeast extracts or are produced with fermentation, although the trigger may be complex and not always the yeast protein itself.
IgG is not the same as Candida testing
This test does not diagnose Candida infection or invasive fungal disease. If you have concerns about recurrent infections, immune compromise, or severe symptoms, you need clinician-directed evaluation that may include cultures, imaging, or other targeted tests.
What do my Yeast F45 IgG results mean?
Low Yeast F45 IgG
A low result generally means the lab did not detect a meaningful IgG response to yeast, or it was below the lab’s reporting threshold. If yeast-containing foods still seem to trigger symptoms, a low IgG does not rule that out, because symptoms can be driven by other mechanisms such as fermentation byproducts, histamine content, FODMAP load, gluten/wheat components, or non-immune intolerance. In that case, your next step is usually a symptom-based trial or broader evaluation rather than assuming yeast is “cleared.”
In-range (or negative) Yeast F45 IgG
An in-range or negative result suggests there is no strong IgG signal to yeast at the time of testing. Many people fall here even if they eat yeast-containing foods regularly. If you feel well and have no consistent pattern with yeast foods, this result is typically reassuring and you may not need to retest unless your symptoms or diet change substantially.
High Yeast F45 IgG
A high result means your immune system shows a stronger IgG recognition of yeast proteins. This can happen because of frequent exposure, because yeast-containing foods are a trigger for you, or both. The most useful way to act on a high result is to run a time-limited, clearly defined elimination (often a few weeks) followed by a planned reintroduction while tracking symptoms, rather than avoiding yeast indefinitely. If symptoms are significant or persistent, it is also worth checking for other common drivers (for example, celiac screening, inflammatory markers, or broader food panels) with your clinician.
Factors that influence Yeast F45 IgG
Your usual diet matters: eating more yeast-containing or fermented foods can increase IgG levels without proving intolerance. Timing matters too, because antibodies can lag behind symptom changes, so retesting immediately after a diet change may not show much movement. Gut inflammation, infections, and immune conditions can also shift antibody patterns and make interpretation less straightforward. Different labs may use different methods and cutoffs, so it is best to trend results with the same lab when possible.
What’s included
- Yeast (F45) Igg
Frequently Asked Questions
Is Yeast F45 IgG an allergy test?
No. This test measures IgG antibodies, which are not the antibody type used to diagnose immediate, potentially dangerous food allergies. If you have rapid symptoms like hives, swelling, wheezing, or throat tightness after eating, ask your clinician about IgE testing and allergy evaluation.
Do I need to fast for a Yeast F45 IgG blood test?
Fasting is usually not required for IgG antibody testing. If you are combining this with other labs (like lipids or glucose), follow the fasting instructions for the full set of tests you ordered.
What foods contain yeast that might matter for this test?
Common sources include breads and baked goods made with baker’s yeast, beer and some alcoholic beverages made with fermentation, and foods with yeast extract. Some fermented foods may be tolerated differently person to person because the trigger is not always the yeast protein itself.
Does a high Yeast IgG mean I have Candida overgrowth?
Not by itself. Yeast F45 IgG is typically a food-related antibody test and does not diagnose Candida infection or invasive fungal disease. If you are worried about recurrent infections or severe symptoms, you need clinician-directed testing that is specific to those conditions.
How long should I avoid yeast before retesting?
There is no single universal timeline, but antibody patterns often change slowly. Many people use a structured elimination period of a few weeks to assess symptoms first, and then consider retesting only if the result will change your plan. If you do retest, keeping the same lab method improves comparability.
Can I have symptoms from yeast foods even if my IgG is low?
Yes. Symptoms can come from non-IgG mechanisms such as intolerance to fermentation byproducts, histamine sensitivity, FODMAP-related fermentation, or reactions to other ingredients commonly found alongside yeast (like wheat). If the pattern is strong, a careful elimination-and-rechallenge can still be informative.
What other tests are often considered alongside Yeast F45 IgG?
That depends on your symptoms. People often pair food-related questions with broader food IgG panels, IgE allergy testing when reactions are immediate, and gastrointestinal evaluation (for example, celiac screening or inflammation markers) when symptoms are persistent or severe. PocketMD can help you decide what to discuss with your clinician.