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The blood type diet claims that people should choose foods according to whether they have type O, A, B, or AB blood. Supporters suggest that blood type may influence digestion, metabolism, inflammation, weight, and the way the body responds to specific foods.
The idea is appealing because it appears to offer a simple form of personalized nutrition. However, research has not shown that matching a diet to an individual’s ABO blood group produces better health outcomes. Studies have found that some versions of the diet may improve certain health markers, but those benefits appear to come from eating more whole foods or fewer highly processed foods—not from matching the diet to blood type.1, 2
Blood type is medically important for transfusions, pregnancy care, and other clinical situations. It is not a validated guide to which foods a person should eat. A more useful approach to personalized nutrition considers medical history, dietary preferences, symptoms, medications, activity, family history, and objective health markers such as glucose, cholesterol, iron, and vitamin levels.
Ulta Lab Tests provides access to many relevant laboratory tests directly online where available. Lab results may provide useful information, but they do not replace an examination, diagnosis, or individualized advice from a qualified healthcare professional.
The blood type diet is an eating plan popularized in the 1990s. It proposes that a person’s ABO blood group reflects ancestral patterns that influence digestion and food compatibility.
| Blood Type | Typical Diet Recommendation |
|---|---|
| Type O | A meat-forward, higher-protein diet with vegetables and limited grains or legumes |
| Type A | A predominantly plant-based or vegetarian diet |
| Type B | A mixed diet that may include meat, dairy, grains, fruits, and vegetables |
| Type AB | A combination of the type A and type B plans |
The theory also suggests that lectins—proteins that bind to carbohydrates—may interact differently with each blood type. However, research has not demonstrated clinically meaningful ABO-specific reactions to ordinary dietary lectins that justify the diet’s food lists.2
Direct answer: There is no reliable evidence that matching foods to an ABO blood type improves weight, glucose, cholesterol, inflammation, or other health outcomes more than following the same diet with a different blood type.
A systematic review found no studies demonstrating the proposed health benefits of ABO-based diets. Later studies found that people could experience favorable changes while following certain blood type diet patterns, but the changes were unrelated to whether their actual blood type matched the diet.1, 3
A separate analysis of a plant-based dietary intervention similarly found that blood type did not change the diet’s effects on body weight, body fat, cholesterol, glucose, or A1c.4
ABO blood type is determined by antigens, or identifying substances, on the surface of red blood cells. The Rh factor determines whether blood is considered positive or negative.
These characteristics matter when:
An ABO Group and Rh Type Test identifies whether a person is A, B, AB, or O and whether the person is Rh-positive or Rh-negative. ABO and Rh status are important for transfusions and may also be relevant during pregnancy.5
ABO blood group has also been studied for associations with certain health risks. Association, however, does not mean that a particular blood type causes a disease or requires a particular diet. It also does not prove that eating according to blood type changes the associated risk.
Feeling better after beginning a blood type diet does not necessarily mean that blood type matching caused the improvement.
Many versions of the diet encourage people to:
These changes can affect energy, calorie intake, digestion, blood glucose, triglycerides, and body weight regardless of blood type. In one study, greater adherence to several blood type diet patterns was associated with favorable cardiometabolic markers. Matching those patterns to the participants’ actual ABO genotype provided no additional benefit.2
The practical lesson is that overall diet quality matters more than blood type matching.
Metabolism is influenced by many factors, including body composition, age, genetics, hormones, activity, sleep, medications, calorie intake, and health conditions. ABO type has not been validated as a stand-alone measure of metabolic function.
Markers such as Hemoglobin A1c, Glucose, Lipid Panel, and—in selected situations—an Insulin Test provide more direct information about metabolic health.
Whole grains and legumes can provide fiber, vitamins, minerals, and plant protein. Individual tolerance varies, but ABO type alone is not a medical reason to eliminate these foods.
Someone with symptoms after eating wheat may need evaluation for celiac disease, wheat allergy, another digestive disorder, or non-celiac sensitivity. These are different concerns and should not be assumed from blood type. A Celiac Disease Comprehensive Panel may be appropriate when symptoms or risk factors support testing.
A thoughtfully planned vegetarian diet can meet nutritional needs, but blood type A does not establish a medical need to avoid meat.
People reducing or eliminating animal foods should pay particular attention to vitamin B12, iron, protein, zinc, iodine, calcium, and vitamin D. Vitamin B12 is naturally present mainly in animal-derived foods and is essential for blood and nerve health.7 Relevant testing may include a Complete Blood Count with Differential and Platelets, Ferritin Test, Iron and Total Iron Binding Capacity Test, and Vitamin B12 and Folate Panel.
Lactose digestion depends primarily on intestinal lactase activity, not ABO blood group. Milk allergy, lactose intolerance, and digestive discomfort from dairy are separate concerns that require different evaluations.
The ABO Group and Rh Type Test provides valuable medical information, but it does not measure glucose control, cholesterol, inflammation, nutrient status, food allergy, or digestive function.
Meaningful nutrition personalization requires a broader assessment of health goals, symptoms, clinical history, food intake, and relevant laboratory findings.
A blood type diet may eliminate foods even when there is no medical reason to avoid them. The more foods or food groups a person removes, the more carefully nutritional adequacy should be considered.
Potential concerns include:
Iron is required for hemoglobin, the protein in red blood cells that transports oxygen. Vitamin B12 supports normal blood-cell formation and nervous-system function.7, 8
Laboratory testing may help identify certain deficiencies, but results should not be used to justify indiscriminate supplementation or unnecessary dietary restriction.
Symptoms sometimes attributed to eating the “wrong foods” for a blood type may have many possible causes.
| Symptom or Risk Factor | What It May Suggest | Related Lab Tests |
|---|---|---|
| Persistent fatigue or reduced exercise tolerance | Anemia, iron deficiency, B12 deficiency, thyroid dysfunction, glucose abnormalities, inadequate calorie intake, or another concern | Complete Blood Count with Differential and Platelets, Ferritin Test, Iron and Total Iron Binding Capacity Test, Vitamin B12 and Folate Panel, Comprehensive Metabolic Panel, Hemoglobin A1c, and TSH Test when appropriate |
| Numbness, tingling, or balance changes | Possible vitamin B12 deficiency or a neurologic concern | Vitamin B12 and Folate Panel, Complete Blood Count with Differential and Platelets, and Methylmalonic Acid Test when appropriate |
| Pale skin, shortness of breath, brittle nails, or hair shedding | Possible anemia or iron deficiency | Complete Blood Count with Differential and Platelets, Ferritin Test, and Iron and Total Iron Binding Capacity Test |
| Frequent thirst, urination, hunger, or unexplained glucose concerns | Possible abnormal glucose regulation | Hemoglobin A1c, Glucose Test, and Comprehensive Metabolic Panel |
| Bloating, diarrhea, constipation, or abdominal discomfort | Celiac disease, lactose intolerance, irritable bowel syndrome, infection, inflammatory disease, or another digestive concern | Celiac Disease Comprehensive Panel when appropriate; other tests based on symptoms and clinical history |
| Symptoms after eating wheat | Celiac disease, wheat allergy, or non-celiac sensitivity | Celiac Disease Comprehensive Panel and targeted food-specific IgE testing when an immediate allergy is suspected |
| Hives, swelling, wheezing, or vomiting shortly after a food | Possible IgE-mediated food allergy | History-directed food-specific IgE testing and evaluation by a qualified healthcare provider or allergist |
| Family history of premature cardiovascular disease | Inherited or acquired cardiometabolic risk | Lipid Panel, Cardio IQ Apolipoprotein B Test, Lipoprotein (a) Test, and Hemoglobin A1c as appropriate |
| Major reduction in meat or animal foods | Potential iron or vitamin B12 shortfall | Complete Blood Count with Differential and Platelets, Ferritin Test, Iron and Total Iron Binding Capacity Test, and Vitamin B12 and Folate Panel |
| Major reduction in dairy or fortified foods | Potential vitamin D or calcium-related concerns | Vitamin D 25-Hydroxy Total Test and Comprehensive Metabolic Panel for serum calcium context |
Safety note: Seek urgent medical care for trouble breathing, swelling of the tongue or throat, fainting, severe chest pain, signs of stroke, significant gastrointestinal bleeding, or other severe or rapidly worsening symptoms.
Laboratory testing cannot identify one perfect diet. It can, however, provide objective information about how the body is functioning and whether a dietary pattern may be associated with measurable concerns.
Depending on the tests selected, laboratory results may provide information about:
A blood test cannot independently determine:
Lab values must be considered alongside symptoms, medical history, food intake, medications, supplements, recent illness, and other health information.
A single value is a snapshot. Comparing results over time may be more informative when evaluating a meaningful dietary change.
The timing of follow-up depends on the marker. For example, Hemoglobin A1c reflects average glucose exposure over approximately two to three months, while cholesterol, triglycerides, blood counts, and nutrient markers may respond on different timelines. Retesting should be based on the initial result, the degree of dietary change, health risks, and professional guidance.
| Lab Test or Biomarker | What It Measures | Why It May Be Relevant | What an Abnormal Result May Generally Suggest | Important Limitations |
|---|---|---|---|---|
| ABO Group and Rh Type Test | A, B, AB, or O blood group and Rh status | Useful for personal medical records, transfusion safety, and pregnancy-related care | Identifies blood group; it does not indicate dietary needs | Not a metabolic, nutrient, allergy, or food-tolerance test |
| Complete Blood Count with Differential and Platelets | Red cells, white cells, platelets, hemoglobin, hematocrit, and red-cell indices | Helps assess anemia and general blood-cell status | Low hemoglobin may indicate anemia; red-cell indices can help guide further evaluation | Does not identify the cause of anemia by itself |
| Comprehensive Metabolic Panel | Glucose, electrolytes, proteins, kidney markers, liver enzymes, and calcium | Provides a broad health baseline during substantial dietary changes | Abnormalities may reflect medical, medication, hydration, or nutritional factors | Serum calcium does not directly measure dietary calcium intake or bone stores |
| Hemoglobin A1c | The percentage of glycated hemoglobin, reflecting average glucose over approximately two to three months | Helps assess longer-term glucose regulation | Higher values may fall into prediabetes or diabetes ranges | Anemia, altered red-cell turnover, pregnancy, kidney disease, and hemoglobin variants may affect interpretation |
| Lipid Panel | Total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides | Helps assess cardiometabolic risk and response to changes in diet, weight, and activity | High LDL or triglycerides may increase cardiovascular concern depending on the full risk profile | Should be interpreted with age, blood pressure, smoking status, family history, diabetes status, and other factors |
| Ferritin Test | Stored iron | Useful when iron intake is reduced or symptoms suggest deficiency | Low ferritin often supports depleted iron stores; high ferritin can occur with inflammation or iron overload | Ferritin may rise during infection, inflammation, liver disease, or other conditions |
| Iron and Total Iron Binding Capacity Test | Circulating iron, transport capacity, and transferrin saturation | Adds context to ferritin and CBC findings | Patterns may support iron deficiency or other iron-related concerns | Serum iron varies and should not be interpreted alone |
| Vitamin B12 and Folate Panel | Blood concentrations of two vitamins needed for blood-cell production and neurologic function | Particularly relevant when animal foods are restricted or absorption is impaired | Low levels may contribute to anemia or neurologic symptoms | Borderline B12 results may require a Methylmalonic Acid Test or other follow-up |
| Vitamin D 25-Hydroxy Total Test | The primary circulating indicator used to assess vitamin D status | May be useful when intake, sun exposure, absorption, or bone health is a concern | Low results may indicate inadequate vitamin D status | Thresholds and supplement decisions require clinical context; more is not always better |
| Insulin Test | Insulin concentration in the blood | Sometimes used with glucose and other markers when insulin resistance is being evaluated | High fasting values may occur with compensatory hyperinsulinemia | No single universal cutoff diagnoses insulin resistance; the test is not necessary for everyone |
| High-Sensitivity C-Reactive Protein Test | Low concentrations of C-reactive protein | May contribute to cardiovascular risk assessment in selected individuals | Elevation may reflect low-grade inflammation or a temporary inflammatory process | Nonspecific; infection, injury, obesity, and chronic inflammatory conditions can raise it |
| Cardio IQ Apolipoprotein B Test | ApoB, which reflects the number of atherogenic lipoprotein particles | May provide added cardiovascular-risk information in selected people | A higher result may indicate more atherogenic particles | Not necessary for every person and should be interpreted with the standard lipid profile |
| Lipoprotein (a) Test | Lipoprotein(a), an inherited lipoprotein particle associated with cardiovascular risk | May be useful with a family history of premature cardiovascular disease or unexplained risk | Higher levels may indicate additional inherited cardiovascular risk | It does not measure whether a diet is matched to blood type |
| Celiac Disease Comprehensive Panel | Antibodies associated with celiac disease, with the exact markers depending on the panel | Appropriate when symptoms or risk factors raise concern for celiac disease | Positive antibodies may support the need for specialist evaluation and possible additional testing | Testing may be less reliable after gluten has already been removed |
| Food-Specific IgE Testing | IgE antibodies directed toward selected foods | May help assess suspected immediate food allergy when supported by a reaction history | A positive result indicates sensitization, not necessarily a clinical allergy | Broad panels can produce false positives and lead to unnecessary food avoidance |
Celiac testing is most informative when a person is still eating gluten. The tissue transglutaminase IgA test is commonly used as an initial serologic test, with total IgA and other markers added when appropriate.6
Food allergy testing should be selected according to symptoms and clinical history. Broad, randomly selected food panels can overidentify sensitization because positive IgE results may occur in people who tolerate the food.10
Not everyone needs every test. Testing should be selected according to dietary changes, symptoms, health goals, risk factors, and prior results.
These tests provide broad information about blood-cell status, glucose, cholesterol, liver markers, kidney markers, proteins, and electrolytes.
Consider targeted nutrient evaluation when a diet removes major food groups or symptoms suggest a deficiency:
Testing may be especially relevant when meat, fish, eggs, dairy, fortified foods, or many grains are substantially restricted.
Depending on personal and family history, a healthcare provider may consider:
These tests are not necessary for everyone. They may provide additional context when standard markers do not fully explain risk or when there is a strong family history of premature cardiovascular disease.
Do not begin a gluten-free diet before celiac testing without discussing the timing with a healthcare provider. Removing gluten can reduce antibody levels and make testing less informative.6
Follow-up testing depends on:
Hemoglobin A1c generally requires enough time to reflect changes in average glucose exposure. Cholesterol, iron, blood counts, and vitamin markers may require different follow-up intervals. Automatic testing every few weeks is not appropriate for every marker or every person.
A laboratory reference range describes the values found in a defined comparison population. A result outside that range may warrant attention, but it does not automatically establish a disease.
Likewise, a result inside the range does not rule out every health concern.
The word “optimal” is often used in wellness marketing, but there is no single universally accepted optimal range for every biomarker or every person.
Clinical interpretation may depend on:
Review the complete report with a qualified healthcare provider before making major dietary, supplement, or medical decisions.
Testing may be reasonable when:
Testing is not a substitute for a dietary assessment. A registered dietitian can help evaluate food quality, protein intake, fiber, calorie adequacy, and potential nutrient gaps that may not be visible on routine laboratory testing.
Preparation depends on the tests ordered.
Review the preparation instructions for every test. Bring the required laboratory requisition, identification, and any other documents listed in the collection instructions.
Ulta Lab Tests allows patients to order many laboratory tests directly online where available. Testing is performed through established laboratory networks, such as Quest Diagnostics where applicable.
Patients can:
Ulta Lab Tests offers access to laboratory information—not a diagnosis or treatment plan. Results may help patients ask better questions and have more informed conversations with their healthcare providers.
Explore relevant testing: Review the Nutrition Tests, Vitamin and Mineral Tests, Diabetes Tests, Heart and Cardiovascular Tests, and Digestive System Tests available through Ulta Lab Tests.
Current evidence does not support the claim that people receive additional health benefits by matching their food choices to ABO blood type. Some versions of the diet emphasize beneficial habits such as eating vegetables and reducing processed foods. However, studies have found that favorable changes occur independently of whether the person follows the plan assigned to their actual blood type.1, 2
The blood type diet typically recommends a meat-forward plan for type O, a plant-based plan for type A, a mixed diet that includes dairy for type B, and a combined A/B pattern for type AB. These categories are based on the diet’s theory rather than validated clinical evidence. Food choices should instead reflect nutritional needs, health risks, symptoms, preferences, and medical guidance.
ABO blood type cannot reliably identify foods that will cause weight gain, inflammation, digestive symptoms, or nutrient problems. Foods should generally be restricted when there is a clear reason, such as a confirmed allergy, diagnosed celiac disease, medically evaluated intolerance, personal preference, ethical choice, or another health consideration—not simply because of blood type.
The most relevant tests depend on the planned diet and personal risk factors. A Complete Blood Count with Differential and Platelets, Comprehensive Metabolic Panel, Hemoglobin A1c, and Lipid Panel can provide broad baseline information. Ferritin, Iron and Total Iron Binding Capacity, Vitamin B12 and Folate, and Vitamin D 25-Hydroxy may be useful when major food groups are removed.
Knowing your blood type can be useful for your medical records, but it will not show which diet is best for you. The ABO Group and Rh Type Test is clinically relevant for transfusion compatibility and pregnancy-related care. It does not assess metabolism, food tolerance, nutrient status, blood sugar, or cardiovascular risk.5
Lab testing can show changes in selected health markers, such as Hemoglobin A1c, cholesterol and triglycerides, liver enzymes, blood counts, iron status, or vitamin levels. It cannot determine whether a diet is ideal in every respect. Energy, hunger, digestion, blood pressure, sleep, physical performance, nutrient adequacy, enjoyment, and sustainability should also be considered.
Not as a general screening tool. Food-specific IgE testing is most useful when symptoms and timing suggest an immediate allergic reaction. Broad panels can produce positive results in people who tolerate the foods, potentially leading to unnecessary avoidance. Testing should be directed by the reaction history and interpreted by a qualified healthcare professional or allergist.10
Most food intolerances are not identified by routine blood testing. Lactose intolerance, for example, may be evaluated through history, dietary trials, or breath testing. Celiac disease involves specific antibody tests and may require intestinal biopsy. Food-specific IgE testing evaluates allergic sensitization, which is different from intolerance.
Testing should be individualized, but commonly considered markers include a Complete Blood Count with Differential and Platelets, Ferritin Test, Iron and Total Iron Binding Capacity Test, Vitamin B12 and Folate Panel, and Vitamin D 25-Hydroxy Total Test. Vitamin B12 deserves particular attention because natural food sources are mainly animal-derived.7
There is no single schedule for every test. Hemoglobin A1c reflects approximately two to three months of glucose exposure, while lipids, blood counts, iron markers, and vitamins may require different intervals. Follow-up timing should reflect the original result, symptoms, degree of dietary change, medications, supplements, and recommendations from a healthcare provider.
Ulta Lab Tests allows patients to order many tests directly online where available. Options may include metabolic, cardiovascular, blood-count, iron, vitamin, and digestive-health tests. Direct access does not replace medical care. Unexpected, significantly abnormal, or difficult-to-interpret results should be reviewed with a qualified healthcare provider.
A stronger approach is to choose a balanced eating pattern based on health goals, medical history, cultural preferences, food access, and sustainability. Mediterranean-style and other plant-forward patterns emphasize vegetables, fruit, whole grains, legumes, nuts, healthy fats, and appropriate protein sources. Laboratory trends and professional guidance can then help refine the plan without relying on ABO-based food rules.
The blood type diet offers an easy-to-understand promise: eat according to your ABO group and improve your health. The available research, however, does not support that promise. Blood type is essential medical information for transfusion and pregnancy-related care, but it is not a validated nutrition prescription.
People who feel better on a blood type diet may be responding to higher diet quality, fewer ultra-processed foods, improved meal planning, or another lifestyle change. Those benefits do not require matching foods to type O, A, B, or AB.
A more useful approach to personalized nutrition combines symptoms, medical history, food intake, health goals, and carefully selected laboratory tests. Ulta Lab Tests provides direct access to many relevant tests, including metabolic, cardiovascular, blood-count, iron, vitamin, and digestive-health markers.
Explore relevant lab tests at UltaLabTests.com, follow the preparation instructions for each test, and review your results with a qualified healthcare provider before making significant dietary, supplement, or medical decisions.
The blood type diet is an eating plan that assigns foods according to ABO blood groups O, A, B, and AB. Scientific studies have not shown that matching a diet to blood type improves health outcomes more than following the same eating pattern without regard to blood type.
Related lab tests: ABO Group and Rh Type Test, Complete Blood Count with Differential and Platelets, Comprehensive Metabolic Panel, Hemoglobin A1c, Lipid Panel, Ferritin Test, Iron and Total Iron Binding Capacity Test, Vitamin B12 and Folate Panel, Vitamin D 25-Hydroxy Total Test, Celiac Disease Comprehensive Panel, Cardio IQ Apolipoprotein B Test, Lipoprotein (a) Test, Insulin Test, and High-Sensitivity C-Reactive Protein Test when appropriate.
Ulta Lab Tests helps patients access many relevant laboratory tests directly online where available, with transparent pricing and secure online results.
Laboratory testing is informational and should be interpreted with a qualified healthcare provider.
This test identifies ABO blood group and Rh status. It does not determine which foods a person should eat.
Celiac testing is symptom- and risk-directed. Testing is generally more informative while the patient is still consuming gluten. Ulta Lab Tests’ digestive-health materials include celiac serology among the tests used to evaluate appropriate digestive symptoms and nutrient concerns.
Food-specific IgE testing should be selected according to a reproducible reaction history rather than used as a broad screening method to create a diet.
TSH may be considered when symptoms such as persistent fatigue, unexplained weight changes, or temperature sensitivity warrant thyroid evaluation.
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