Sign in →

Test Code LAB10190 Lactose Tolerance



Collection Requirements

8 hour fast is required.

Testing requires patient to remain at laboratory approximately 2 hours.

Prepare 50 gm lactose according to LACTOL package insert.

Draw fasting specimen.

Have patient drink 50 gm of prepared lactose (LACTOL). After patient has completely consumed the lactose load, draw specimens at 15 min, 30 min, 60 min, 90, min and 120 min after lactose dose is consumed.

Primary Collection Container

Green PST (Lithium Heparin)

Alternate Collection Container

Green Microtainer PST


Plasma refrigerated

Preferred Transport Temperature



Centrifuge and separate from cells within 2 hours.


Ambient: 8 hours

Refrigerated: 48 hours

Minimum Testing Volume

0.1 mL

Reference Range

25 mg rise in glucose after injestion of Lactol.


Hexokinase (HK) catalyzes the phosphorylation of glucose in the presence of adenosine-5’-triphosphate (ATP) and magnesium to form glucose-6-phosphate (G-6-P) and adenosine diphosphate (ADP). G-6-P is then oxidized by glucose-6-phosphate dehydrogenase (G-6-PDH) in the presence of nicotinamide adenine dinucleotide (NAD) to produce 6-phosphogluconate and NADH. One mole of NAD is reduced to one mole of NADH for each mole of glucose present. The absorbance due to NADH (and thus the glucose concentration) is determined using a bichromatic (340 and 383 nm) endpoint technique. Siemens Dimension Vista.


Monday – Friday

7:00 am – 3:30 pm


As completed

CPT Codes

82951; 82952×2

Unacceptable Conditions

Non-fasting patient.

Patient vomiting immediately after injestion of Lactol.