Lactase enzyme
Summary
Lactase supplements split lactose before it reaches the colon. In several crossover trials of lactose-intolerant adults, doses of about 9,900–13,500 FCC units cut breath hydrogen and symptoms after a lactose load (grade B). For infant colic, trials disagree and reviews call the evidence inconclusive (grade C).
Key facts
- Single doses of 9,900–13,500 FCC cut breath hydrogen and symptoms in crossover trials of 24–47 adults[1][4]
- About 12–15 g (roughly 1 cup of milk) without supplements, per a 2010 systematic review[6]
- Five trials (391 infants) gave mixed results; one later trial of 162 infants found less crying[7][8]
- Lactose intolerance is not milk allergy, which is an immune reaction to milk protein[10]
- 6 graded human outcomes on this page
- October 13, 2026
How it works
EstablishedLactase splits lactose into glucose and galactose, which the small intestine absorbs. When the body makes too little lactase, undigested lactose reaches the colon and is fermented, producing gas and symptoms. Supplemental lactase, swallowed with dairy or added to milk beforehand, does the splitting for the gut, which shows up as lower breath hydrogen in tests.[9][10][1][2]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
At a glance: strongest evidence per outcome
| Outcome | Grade | Effect | Strongest evidence | Rows |
|---|---|---|---|---|
| Lactose intolerance | Grade B | Improved | Crossover RCT · n = 47 · 2021 | 4 rows |
| Infant colic | Grade C | No effect | Systematic review · n = 391 · 2024 | 2 rows |
Every graded row
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Breath hydrogen and symptoms after a 25 g lactose load | Improved | Grade B | Crossover RCT · n = 47 · 2021 Adults with breath-test-confirmed lactose intolerance (India) Form: Chewable lactase tablets (4,500 FCC units each) · Dose: 3 tablets (13,500 FCC) 5 minutes before 25 g lactose · Duration: Single dose per visit, 1-week washout Symptom scores and breath hydrogen were lower with lactase than placebo; cumulative breath hydrogen over 3 hours fell by 55%. | 33490624 (opens PubMed)Source [1] |
| Breath hydrogen and symptom score after 400 mL milk | Improved | Grade B | Crossover RCT · n = 30 · 2005 Adults with lactose malabsorption and intolerance Form: Kluyveromyces lactis beta-galactosidase added to milk · Dose: 3,000 units added 10 hours before, or 6,000 units 5 minutes before, drinking 400 mL milk · Duration: Single test per condition Both regimens cut peak breath hydrogen (about 12–14 vs 51 ppm with placebo) and cumulative hydrogen, and lowered the symptom score. | 15674309 (opens PubMed)Source [2] |
| Breath hydrogen and symptoms after 50 g lactose in milk | Improved | Grade B | Crossover RCT · n = 24 · 1992 Lactose-intolerant adults Form: Chewable lactase tablets · Dose: 3 tablets (9,900 FCC units) with 50 g lactose · Duration: Single dose per visit, ≥1-week washout Peak breath hydrogen was lower and cramping, belching, flatulence and diarrhoea were rated less severe in the first 8 hours than with placebo. | 1534729 (opens PubMed)Source [4] |
| Crying and fussing time in infant colic | No effect | Grade C | Systematic review · n = 391 · 2024 Infants under 6 months with colic in 5 randomized trials Form: Lactase drops added to milk or feeds · Dose: Varied by trial · Duration: 1–4 weeks Three trials reported less crying, but a meta-analysis of two found no difference in crying or fussing time after 1 week; risk of bias was high in three of the five trials. | 38426798 (opens PubMed)Source [7] |
| Crying or fussing time and days with colic | Improved | Grade C | RCT · n = 162 · 2022 Infants under 5 months with colic (India) Form: Lactase drops (600 FCC units/mL) · Dose: 5 drops in breast milk or formula four times a day · Duration: 4 weeks Crying or fussing fell to about 90 vs 179 minutes a day with placebo, and colic days were fewer; adverse events were similar. | 35922776 (opens PubMed)Source [8] |
| Breath-test normalisation, peak breath hydrogen and symptom score | Improved | Grade C | RCT · n = 60 · 2010 Lactose-intolerant patients Form: Tilactase (also an L. reuteri arm) · Dose: Tilactase 15 minutes before the breath test · Duration: Single dose More patients normalised their breath test with tilactase than placebo, and peak hydrogen and symptoms fell; tilactase outperformed L. reuteri. | 20391953 (opens PubMed)Source [3] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| Lactase tablets or caplets (taken with dairy) | Varies[1][11] | Not absorbed as such; works in the gut. 9,900–13,500 FCC taken with a lactose load lowered breath hydrogen.[1][4] | No safety concerns reported in the single-dose crossover trials cited.[1][4] | Symptoms and breath hydrogen after lactose in adults |
| Lactase drops added to milk | Varies[2] | Adding enzyme 10 hours or 5 minutes before drinking milk cut breath hydrogen by about three-quarters at peak.[2] | Not reported as a problem in the trial cited.[2] | Lactase added to milk before drinking, in adults with lactose malabsorption |
| Lactase drops for infant feeds | Varies[8] | No absorption data; works on lactose in the feed.[8] | Adverse events were similar to placebo over 4 weeks.[8] | Infant colic (evidence mixed) |
Studied doses
Doses studied in human trials ranged from 3,000–6,000 enzyme units added to 400 mL of milk and single doses of 9,900–13,500 FCC units taken with a lactose load, to three tablets a day for 6 weeks in a comparison of two brands.[1][2][4][5]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
None found in our sources.
Who should be careful
- Milk allergy
- Lactase only breaks down milk sugar; it does nothing for milk allergy, which is an immune reaction to milk.[10]
- Infants
- Evidence in infant colic is mixed and partly at high risk of bias, so use in babies is a question for their clinician.[7]
- Persistent digestive symptoms
- Lactose intolerance can follow injury to the small intestine, which may need its own treatment; ongoing symptoms deserve assessment.[9]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
How to read the label
- Units are FCC, not mgTrials dosed lactase in FCC units (about 9,900–13,500 per lactose challenge). One caplet label lists 9,000 FCC; others use acid lactase units (ALU) or milligrams, which cannot be compared directly with FCC.[1][4][11][12]
- Per serving, not per capsuleOne label lists 90 mg of lactase (9,000 ALU) per 3-capsule serving, or 30 mg (3,000 ALU) per capsule, with up to 9 capsules a day.[11]
- TimingTake with the first bite of dairy, or add drops to milk ahead of time; the trials gave enzyme 5–15 minutes before or with the lactose.[9][12][1][2][3]
Frequently asked questions
Do lactase pills work?
Yes, for lactose intolerance in adults: double-blind crossover trials found lower breath hydrogen and fewer symptoms when lactase was taken with a lactose load.[1][2][4]
How much lactase is in the trials?
Single doses of about 9,900–13,500 FCC units with 25–50 g of lactose, or 3,000–6,000 units added to 400 mL of milk.[1][2][4]
When should lactase be taken?
NIDDK describes taking tablets before eating dairy or adding drops to milk; trials gave it just before or with the lactose.[9][1]
Does lactase help infant colic?
Evidence is mixed. A 2024 review of five trials called it inconclusive, though a 2022 trial of 162 infants found less crying.[7][8]
Is lactose intolerance the same as a milk allergy?
No. Milk allergy is an immune system disorder, and lactase does not help it.[10]
Sources
- [1]Effect of lactase on symptoms and hydrogen breath levels in lactose intolerance: A crossover placebo-controlled study.. JGH Open, 2021. crossover-RCT
- [2]Effect of exogenous beta-galactosidase in patients with lactose malabsorption and intolerance: a crossover double-blind placebo-controlled study.. Eur J Clin Nutr, 2005. crossover-RCT
- [3]The effect of oral supplementation with Lactobacillus reuteri or tilactase in lactose intolerant patients: randomized trial.. Eur Rev Med Pharmacol Sci, 2010. RCT
- [4]Effect of a single dose of lactase on symptoms and expired hydrogen after lactose challenge in lactose-intolerant subjects.. Clin Pharm, 1992. crossover-RCT
- [5]ORAL ADMINISTRATION OF EXOGENOUS LACTASE IN TABLETS FOR PATIENTS DIAGNOSED WITH LACTOSE INTOLERANCE DUE TO PRIMARY HYPOLACTASIA.. Arq Gastroenterol, 2016. RCT
- [6]Systematic review: effective management strategies for lactose intolerance.. Ann Intern Med, 2010. systematic-review
- [7]Effect of lactase supplementation on infant colic: Systematic review of randomized controlled trials.. J Pediatr Gastroenterol Nutr, 2024. systematic-review
- [8]Oral lactase for infantile colic: a randomized double-blind placebo-controlled trial.. BMC Pediatr, 2022. RCT
- [9]Treatment for Lactose Intolerance. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), 2018. fact-sheet
- [10]Definition & Facts for Lactose Intolerance. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), 2018. fact-sheet
- [11]Lactase Digest (Source Naturals), DSLD label 274815: 90 mg lactase enzyme (9,000 ALU, acid lactase units) per 3-capsule serving (30 mg, 3,000 ALU per capsule), 1–3 capsules with dairy, no more than 9 capsules daily. NIH Office of Dietary Supplements, Dietary Supplement Label Database, 2022. label
- [12]Fast Acting Lactase (Kirkland Signature), DSLD label 62680: 9,000 FCC lactase units per caplet, one caplet with the first bite of dairy (two if needed). NIH Office of Dietary Supplements, Dietary Supplement Label Database, 2016. label
What changed
- Independent adversarial review: DSLD re-check. Kirkland label 62680 does state 9,000 FCC per caplet (page said no amount); Source Naturals 274815 states 9,000 ALU per 3 capsules. Source titles and label guide corrected.
- Strict adversarial pass: PMIDs re-checked; 2021 trial dose confirmed in the PMC full text (3 × 4,500 FCC). Adult grade B rests on three concordant double-blind crossover trials; infant colic held at C because reviews call it inconclusive.
- First draft rebuilt from scratch after the earlier draft files were lost. Every PMID checked against NCBI esummary and abstracts read for each row; the 2021 trial dose (3 × 4,500 FCC) taken from the PMC full text. Lactase label amounts read from the DSLD API as amounts per serving.