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• Diagnosis and Tests

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Summary

Lactose intolerance means that you cannot digest foods with lactose in them. Lactose is the sugar found in milk and foods made with milk. After eating foods with lactose in them, you may feel sick to your stomach. You may also have:

• Gas
• Diarrhea
• Swelling in your stomach

Your doctor may do a blood, breath or stool test to find out if your problems are due to lactose intolerance.

Lactose intolerance is not serious. Eating less food with lactose, or using pills or drops to help you digest lactose usually helps. You may need to take a calcium supplement if you don't get enough of it from your diet, since milk and foods made with milk are the most common source of calcium for most people.

NIH: National Institute of Diabetes and Digestive and Kidney Diseases

Start Here

• Lactose Intolerance (Mayo Foundation for Medical Education and Research)
• Lactose Intolerance (National Institute of Diabetes and Digestive and Kidney Diseases) Also in Spanish

Diagnosis and Tests

• Food Allergy Testing (National Library of Medicine) Also in Spanish
• Lactose Tolerance Tests (National Library of Medicine) Also in Spanish

Related Issues

• Allergic to Milk? Some Dark Chocolate Labeled as Dairy-Free May Still Contain Milk (Food and Drug Administration) Also in Spanish
• Food Intolerance vs. Food Allergy: What's the Difference? (Mayo Foundation for Medical Education and Research) Also in Spanish
• Milk Allergy (Mayo Foundation for Medical Education and Research)

Genetics

• Lactose intolerance: MedlinePlus Genetics (National Library of Medicine)

Clinical Trials

• ClinicalTrials.gov: Lactose Intolerance (National Institutes of Health)

Journal Articles References and abstracts from MEDLINE/PubMed (National Library of Medicine)

• Article: Gut Microbiota in Lactose Intolerance: A Mendelian Randomization Study on Microbial...
• Article: Lactose Breath Test: Possible Strategies to Optimize Test Performance, Accuracy, and...
• Article: Diagnosis of lactose intolerance: concordance between 13910-C/T genotype and lactose tolerance...
• Lactose Intolerance -- see more articles

Find an Expert

• National Institute of Diabetes and Digestive and Kidney Diseases

Children

• Dairy-Free Diet (For Parents) (Nemours Foundation) Also in Spanish
• Lactose Intolerance (For Kids) (Nemours Foundation) Also in Spanish
• Lactose Intolerance (For Parents) (Nemours Foundation) Also in Spanish

Teenagers

• Lactose Intolerance (Boston Children's Hospital) Also in Spanish
• Lactose Intolerance (For Teens) (Nemours Foundation) Also in Spanish

Women

• Lactose Intolerance (Department of Health and Human Services, Office on Women's Health) Also in Spanish

Patient Handouts

• Lactose intolerance (Medical Encyclopedia) Also in Spanish