Casein F78 IgG test (milk protein antibody)
It measures IgG antibodies to casein (milk protein) to support food-sensitivity discussions, 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 Casein F78 IgG test looks for IgG antibodies your immune system has made to casein, a major protein in cow’s milk. People usually order it when they are trying to connect symptoms to dairy exposure, or when they are planning a structured elimination and reintroduction.
This test is different from classic “milk allergy” testing. IgG results do not diagnose an allergy, and they do not prove that casein is the cause of your symptoms on their own. They can, however, add a data point that you and your clinician can use alongside your history, diet pattern, and other labs.
If you already have immediate reactions to dairy (hives, wheezing, throat tightness, vomiting, or anaphylaxis), you should prioritize IgE-based allergy evaluation and urgent medical guidance instead of relying on IgG results.
Do I need a Casein F78 IgG test?
You may consider Casein F78 IgG testing if you notice symptoms that seem to track with dairy intake but the pattern is inconsistent or delayed. Common reasons include bloating, abdominal discomfort, stool changes, skin flares, headaches, sinus congestion, or fatigue that you suspect might worsen after milk, cheese, yogurt, or “hidden dairy” ingredients.
This test can also be useful if you are trying to make an elimination diet more structured. Having a baseline result can help you decide whether to focus your trial on casein-containing foods specifically, and it can give you a reference point if you retest after a sustained change in exposure.
You may not need this test if your main concern is lactose intolerance. Lactose intolerance is caused by low lactase enzyme activity, not an immune response to milk proteins, so breath testing or a dietary trial often fits better.
If you are pregnant, have autoimmune disease, take immune-modifying medications, or have a history of severe allergic reactions, it is especially important to interpret results with a clinician. Testing is meant to support clinician-directed care and shared decision-making, not self-diagnosis.
This is a laboratory-developed immunoassay performed in a CLIA-certified lab; results are not a standalone diagnosis and should be interpreted in clinical context.
Lab testing
Order Casein F78 IgG through Vitals Vault and schedule your blood draw when it works for you.
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 Casein F78 IgG testing without a separate doctor visit, and then complete your blood draw at a participating lab location. Your report is designed to be easy to share with your clinician so you can decide what the result means for your symptoms and diet.
If you want help turning a number into next steps, PocketMD can walk you through common interpretation questions, like whether your symptoms fit an immune-mediated pattern, what companion tests might clarify the picture, and when retesting is reasonable.
You can also use Vitals Vault to broaden the workup when needed. For example, if you are unsure whether dairy is the issue versus another food trigger or a non-food cause, you can add related allergy or health panels and keep everything in one place for trend tracking over time.
- Order online and schedule your draw at a participating lab site
- Clear, shareable results you can review with your clinician
- PocketMD support for interpretation and follow-up planning
Key benefits of Casein F78 IgG testing
- Adds an objective data point when you suspect dairy-related symptoms but the timing is delayed or inconsistent.
- Helps you distinguish “milk protein” questions (casein) from lactose intolerance, which is a separate mechanism.
- Can guide a more targeted elimination and reintroduction plan focused on casein-containing foods.
- Provides a baseline you can compare against if you change exposure and want to retest later.
- Supports conversations about broader immune reactivity when paired with other food IgG or allergy testing.
- May reduce guesswork when you are tracking multi-system symptoms such as GI issues plus skin or sinus flares.
- Pairs well with PocketMD-style interpretation so you can connect the result to practical next steps and companion labs.
What is Casein F78 IgG?
Casein is a family of proteins found in mammalian milk, and it makes up a large portion of the protein in cow’s milk. “F78” is a lab allergen code used to identify casein as the target antigen in testing.
IgG (immunoglobulin G) is a class of antibodies your immune system can produce after exposure to a substance, including foods. A Casein F78 IgG test measures the amount of IgG antibodies in your blood that bind to casein.
An important nuance is that IgG antibodies can reflect exposure and immune recognition, and they do not automatically mean you have a harmful reaction. Some people with frequent dairy intake can have measurable IgG without symptoms, while some symptomatic people may have low or negative IgG. That is why your result is most useful when it is interpreted alongside your symptom pattern, your diet history, and (when appropriate) other tests.
IgG vs IgE: why the distinction matters
IgE antibodies are associated with immediate-type allergic reactions that can be dangerous. IgG antibodies are not the same thing, and an IgG result should not be used to rule in or rule out an IgE-mediated milk allergy. If you have rapid-onset symptoms after dairy (minutes to a couple of hours), talk with a clinician about IgE testing and safety planning.
Casein vs lactose intolerance
Lactose intolerance happens when you do not digest lactose well, leading to gas, bloating, and diarrhea after lactose-containing foods. Casein is a protein, not a sugar. A casein-focused test is aimed at immune recognition of milk protein, while lactose intolerance is usually evaluated with a dietary trial, lactose breath testing, or clinical history.
How clinicians often use the result
In practice, clinicians may use Casein IgG as one piece of a broader puzzle. It can help decide whether a time-limited elimination is worth trying, whether to look for other food triggers, or whether symptoms are more likely explained by non-food causes such as IBS, reflux, infections, medication effects, or stress-related gut changes.
What do my Casein F78 IgG results mean?
Low Casein F78 IgG
A low or negative result means the lab did not detect much IgG binding to casein at the time of testing. This can happen if you rarely consume dairy, if you have been avoiding it, or if your immune system simply does not produce measurable IgG to casein. If your symptoms strongly track with dairy anyway, a low result does not fully rule out intolerance, non-IgG immune reactions, or other mechanisms such as lactose intolerance.
In-range / typical Casein F78 IgG
Many labs report IgG on a scale where “normal” can include low-level positivity, especially in people who eat dairy regularly. A typical result often suggests exposure and immune recognition without proving clinical sensitivity. If you feel well with dairy, a midrange result is usually not a reason to restrict foods on its own. If you have symptoms, the value is in comparing the result with your symptom timing and in planning a careful trial rather than making assumptions.
High Casein F78 IgG
A high result means your blood shows stronger IgG reactivity to casein. This can be seen with frequent exposure, increased immune activation, or a pattern that may align with symptoms in some people. It still does not diagnose a milk allergy, and it does not prove that casein is the root cause of your symptoms. If you and your clinician decide to act on a high result, the most practical next step is usually a time-limited elimination followed by a structured reintroduction to see whether symptoms change in a reproducible way.
Factors that influence Casein F78 IgG
Your recent diet matters: regular dairy intake can raise IgG levels, while avoidance for weeks to months can lower them. Immune status can also shift results, including acute illness, chronic inflammation, pregnancy, and medications that suppress or modify immune function. Lab methods and reporting categories vary, so the same numeric value may not map perfectly across different laboratories. Finally, symptoms can be driven by multiple triggers at once, so it helps to interpret this marker alongside your overall clinical picture rather than in isolation.
What’s included
- Casein (F78) Igg
Frequently Asked Questions
Is Casein F78 IgG the same as a milk allergy test?
No. A milk allergy is typically evaluated with IgE-based testing and clinical history, because IgE is associated with immediate allergic reactions. Casein F78 IgG measures IgG antibodies to a milk protein and is not used to diagnose or rule out an IgE-mediated allergy.
Do I need to fast for a Casein IgG blood test?
Fasting is usually not required for IgG antibody testing. If you are combining this test with other labs (like lipids or glucose/insulin markers), follow the fasting instructions for the full set of tests you are ordering.
If my Casein IgG is high, should I stop eating dairy?
A high result can be a reason to consider a structured, time-limited elimination and reintroduction, ideally with clinician guidance. It is not proof that dairy is harmful for you, and long-term restriction without a clear symptom benefit can make diet quality harder. The most helpful approach is to test a clear hypothesis and track symptoms carefully.
Can I have dairy symptoms with a negative Casein IgG?
Yes. Symptoms after dairy can come from lactose intolerance, other milk proteins, non-immune mechanisms, or unrelated GI conditions. A negative IgG result means low measured IgG reactivity to casein, but it does not rule out other explanations for your symptoms.
How long should I avoid dairy before retesting Casein IgG?
There is no single universal timeline, because IgG levels can change gradually and depend on your baseline exposure and immune activity. Many people discuss retesting after several weeks to a few months of consistent avoidance or a clear change in intake. If you are using the test to guide an elimination trial, your symptom response during the trial is often more actionable than the exact retest date.
What is the difference between casein and whey testing?
Casein and whey are different milk protein fractions. Some people react more to one than the other, so testing can be more specific when both are considered. If you are trying to pinpoint which dairy components may be relevant, ask your clinician whether adding whey-related markers or broader dairy testing makes sense.