Lactose Tolerance Test

Synonym/Acronym

LTT.

Rationale

To assess for lactose intolerance or other metabolic disorders.

Patient Preparation

For the breath test or the glucose challenge test, there are no fluid restrictions unless by medical direction. Inform the patient that antibiotics, laxatives, antacids, and stool softeners should not be taken within 2 wk prior to the test. Fasting for at least 12 hr before the test is required, and strenuous activity should also be avoided for at least 12 hr before the test. The patient should be instructed not to smoke cigarettes or chew gum during the test. Instructions for the breath test may also include brushing the teeth and/or rinsing the mouth with water prior to and during the breath test. Obtain the pediatric patient’s weight to calculate dose of lactose to be administered. Protocols may vary among facilities.

Normal Findings

Method: Spectrophotometry for blood.

Hydrogen Breath Test	Increase of less than 20 parts per million over the baseline measurement is considered normal
Blood Test	Change in Blood Glucose Value* Conventional Units	SI Units (Conventional Units × 0.0555)
Normal	Greater than 20–30 mg/dL above fasting level	Greater than 1.1–1.7 mmol/L above fasting level
Inconclusive	20–30 mg/dL above fasting level	1.1–1.7 mmol/L above fasting level
Abnormal	Less than 20 mg/dL above fasting level	Less than 1.1 mmol/L above fasting level
Stool Test	pH may vary but is normally alkaline

^* Compared to fasting sample for infants, children, adults, and older adults.

Critical Findings and Potential Interventions ⬆ ⬇

Glucose

Adults and children

Less than 40 mg/dL (SI: Less than 2.22 mmol/L)
Greater than 400 mg/dL (SI: Greater than 22.2 mmol/L).

Timely notification to the requesting health-care provider (HCP) of any critical findings and related symptoms is a role expectation of the professional nurse. A listing of these findings varies among facilities.

Consideration may be given to verification of critical findings before action is taken. Policies vary among facilities and may include requesting immediate recollection and retesting by the laboratory or retesting using a rapid point-of-care testing instrument at the bedside, if available.

Symptoms of decreased glucose levels include headache, confusion, polyphagia, irritability, nervousness, restlessness, diaphoresis, and weakness. Possible interventions include oral or IV administration of glucose, IV or intramuscular injection of glucagon, and continuous glucose monitoring.

Symptoms of elevated glucose levels include abdominal pain, fatigue, muscle cramps, nausea, vomiting, polyuria, polyphagia, and polydipsia. Possible interventions include fluid replacement in addition to subcutaneous or IV injection of insulin with continuous glucose monitoring.

Overview ⬆ ⬇

(Study type: Breathalyzer for hydrogen breath test; plasma collected in a gray-top [fluoride/oxalate] tube for blood; stool sample for stool pH related body system: Digestive system.)

Lactose is a disaccharide found in dairy products. When ingested, lactose is broken down in the intestine by the sugar-splitting enzyme lactase into glucose and galactose. When sufficient lactase is not available, intestinal bacteria metabolize the lactose, resulting in abdominal bloating, pain, flatus, and diarrhea. The most commonly used method to determine lactose intolerance is accomplished using the noninvasive hydrogen breath test. The breakdown of lactose by intestinal bacteria produces hydrogen gas. Before the administration of lactose, the patient breathes into a balloon. The concentration of hydrogen is measured from a sample of the gas in the balloon. After the administration of lactose, the patient breathes into a balloon at 15-min intervals over a period of 2 to 3 hr, and subsequent samples are measured for levels of hydrogen gas. The breath test is considered abnormal if the hydrogen measurements increase over the fasting or pretest level.

The blood tolerance test screens for lactose intolerance by monitoring glucose levels after ingestion of a dose of lactose. There is also a stool acidity test used for pediatric patients who may not be able to be tested by the breath or glucose blood methods. After administration of a lactose solution, a stool sample is collected and tested for acidity. Normally, stool has a neutral or slightly alkaline pH. If the patient is unable to metabolize the lactose into glucose and galactose, lactic acid (and other acids) will be excreted in the stool, and the stool pH will be acidic.

Indications ⬆ ⬇

Evaluate patients for suspected lactose intolerance.

Interfering Factors ⬆ ⬇

Breath test

Patients will be given specific instructions regarding preparation for the breath test. Nonadherence to the protocol prior to or during the procedure will invalidate the results. Protocals may vary from facility to facility.

Blood study

Numerous medications may alter glucose levels (see study titled “Glucose”).
Delayed gastric emptying may decrease glucose levels.
Smoking may falsely increase glucose levels.

Potential Medical Diagnosis: Clinical Significance of Results ⬆ ⬇

Glucose Levels Increased In

Normal response

Glucose Levels Decreased In

Lactose intolerance (lactase is insufficient to break down ingested lactose into glucose)

Nursing Implications ⬆

Potential Problems: Assessment & Nursing Diagnosis/Analysis

Problems		Signs and Symptoms
Gastrointestinal (altered—related to gastric irritation secondary to bowel irritation from undigested lactose)		Frequent diarrhea after ingesting dairy products with lower abdominal cramping, gas, bloating
Pain (related to altered gastrointestinal [GI] motility secondary to lactase deficiency)		Lower abdominal cramping, gas, bloating, diarrhea

Before the Study: Planning and Implementation

Teaching the Patient What to Expect

Review the procedure with the patient.
Discuss how this test can assist with evaluating tolerance to dairy products that contain lactose.
For the glucose blood test, hydrogen breath test, or stool acidity test, lactose will be dissolved in a small amount of room temperature water (250 mL) and administered over a 5- to 10-min period.
Dosages are calculated based on weight and are determined at the discretion of the requesting HCP. Blood test—2 g/kg body weight to a maximum of 50 g; Breath test—up to a maximum of 25 g; for patients of all ages. Example: First convert the patient’s weight in pounds to kilograms. One pound is equal to 0.45 kg; therefore, a weight of 50 lb is equal to 22.7 kg. The appropriate dosage of lactose in this example would be 22.7 × 2 = 45.4 g. Lower challenge doses may be used in cases of suspected severe lactose intolerance.
Record body weight, dose administered, and time of ingestion. Explain that the test may produce symptoms such as cramps and diarrhea. Record any symptoms the patient reports throughout the course of the test.
Glucose Blood Sample: A baseline specimen will be collected with additional samples collected every 15 min over a 120-min interval; at 15, 30, 60, 90, and 120 min.
Hydrogen Breath Test: A baseline specimen will be collected followed by administration of a lactose solution; additional samples are collected every 15 min over an interval of 2 to 3 hr. Breath samples are collected by blowing into a collection device that resembles a balloon.
Stool pH test: A stool specimen is collected, and pH is analyzed.

After the Study: Implementation & Evaluation Potential Nursing Actions

Avoiding Complications

Ensure the patient understands that the preparation designed for this test may cause cramping and diarrhea ranging in intensity from mild to severe.

Treatment Considerations

Gastrointestinal

There are some interventions that can help when the patient has diarrhea.
Interventions/actions include the following: Eliminate or reduce the consumption of dairy products. Self-administer an oral enzyme medication (lactase liquid, capsules, or tablets) to manage lactose when ingested.

Pain

Pain associated with lactose intolerance can be a concern.
Interventions/actions for pain management include the following: Eliminate or reduce the consumption of dairy products. This can do a great deal to prevent the pain experienced with lactose ingestion.

Nutritional Considerations

An accurate history of GI upset with the ingestion of dairy products can be helpful in identifying causal factors. Symptoms of intolerance to dairy products include a history of lower abdominal cramping, gas, bloating, and diarrhea with the ingestion of dairy products.
Interventions/actions related to intolerance include the following: Trial a lactose-free diet to see if the symptoms of GI upset resolve. Avoid milk products and carefully read labels on prepared products. Emphasize the importance of self-administering the oral enzyme medication that manages ingested lactose. Products such as Lactaid tablets or drops may allow ingestion of milk products without sequelae. Many lactose-free food products are now available in grocery stores. Evaluate foods for hidden dairy ingredients, such as found in sherbet, sauces, gravy, and desserts. Yogurt, which contains inactive lactase enzyme, may be ingested. The lactase in yogurt is activated by the temperature and pH of the duodenum and substitutes for the lack of endogenous lactase.

Clinical Judgement

Consider how to get acceptance of limiting or eliminating the consumption of obvious sources of dairy (lactose), such as milk, ice cream, and cheese, as a valuable preventative measure.

Follow-Up Evaluation and Desired Outcomes

Understands that dietary choices will need to be altered if lactose intolerance is identified.
Considers collaboration with a registered dietitian to ensure proper diet selections and nutritional balance.