Lactase is the enzyme your small intestine uses to split lactose, the sugar in milk. Most adults worldwide make less of it after childhood, and a lactase pill taken with dairy supplies the enzyme from outside. The pills on the shelf differ more than their boxes suggest: in dose per tablet, in sweeteners and allergens, and in how much the label tells you.
We compared 17 lactase products sold in the US and ranked six on dose per serving, label clarity, formulation, marketing and cost. For the science behind lactose intolerance and the trials in depth, see our lactose intolerance guide.
The short version
- Best overall: Lactaid Fast Act caplets, with 9,000 FCC units in one caplet, plain ingredients and the lowest cost per dose of our picks.
- Clearest label: Natural Factors, which names the enzyme's source and defines its units. Best vegan: Enzymedica DairyAssist.
- Dose: trials used roughly 3,000 to 9,900 units with the dairy meal, and the EU allows a lactose digestion claim only at 4,500 FCC units or more per meal. Large dairy loads can overwhelm a standard dose.
- Check the inactive ingredients. The chewables contain mannitol, a sugar alcohol, and one capsule here contains wheat.
- No independent testing we could confirm. We found no national-brand lactase with a third-party certification we could confirm on the certifier's site.
How we ranked them
To qualify, a product needed lactase as its main ingredient (we allowed one lactase and protease combination), a Supplement Facts panel we could read on the brand's site or in the NIH label database, lactase activity printed in FCC units, and a US Amazon listing. We did not rank liquid drops, products whose sites show no facts panel, or products that make safety claims we could not support. Two more were not ranked: Lactaid Original Strength, because Lactaid's website gives conflicting strength figures for it, and LactoJoy, because its current US label lists the enzyme in milligrams rather than units. Scoring:
- Dose (20%). Full marks when one tablet or capsule gives 4,500 to about 10,000 units, the range behind the EU claim and the trials.
- Evidence (10%). The same for every product, since all rely on lactase and no trial tested a current product.
- Label transparency (15%). Highest when the panel gives units per tablet and the enzyme's source.
- Verification (10%). No product had a certification we could confirm, so none scored high; a testing seal or claim we could not confirm earned a little more than none.
- Cost (20%), per 9,000 units, from Amazon prices when we reviewed the products.
- Formulation (15%). Points off for sugar alcohols, artificial sweeteners and allergens such as wheat.
- Marketing (10%). Points off for unverifiable superiority, speed claims with no data, and benefit claims beyond the evidence.
What lactase supplements can and cannot do
It works for many people, not all. In a double-blind crossover trial, 24 adults who took three chewable tablets (9,900 FCC units in total) with a large lactose load had lower breath hydrogen, the standard sign of undigested lactose, and fewer cramps and less gas than with placebo. Another trial in 30 adults found lactase added to milk sharply cut breath hydrogen and symptoms. Results vary with the product, the dose and the amount of lactose: in one study, 3,000 to 6,000 units helped with lactose in milk but were overwhelmed by a 50 gram lactose drink, and in a 10-person 1994 comparison one brand lowered breath hydrogen but not symptoms while another eased symptoms. A review commissioned by the US National Institutes of Health judged the evidence for lactose intolerance treatments insufficient, mainly because studies differed so much.
No trial tested a product on this list. The brand-specific studies we found used Lactaid formulas from the 1990s or used Lactaid as a comparison product. That is why every product here gets the same evidence score.
Timing and dose. Lactase works in the gut while the dairy is there, so labels say to take it with the first bite. The EU allows the claim that lactase "improves lactose digestion" only at 4,500 FCC units or more per lactose-containing meal. That NIH review also found most people with lactose intolerance can tolerate about 12 to 15 grams of lactose, roughly the amount in a cup of milk, without a pill.
What it does not do. Lactase does not help a milk protein allergy, and it does not make lactose safe for people with galactosemia, because splitting lactose still releases galactose. Allergic reactions to lactase tablets are rare but have been reported.
The 6 best lactase supplements
Tap any product to jump straight to its full review.
Lactaid Fast Act Caplets (96 caplets)
Best for: Most people who want one pill per meal
One 9,000 FCC caplet, plain ingredients and the lowest cost per dose of our picks. Its box promises more than the trials show.
- 9,000 FCC units in a single caplet, inside the range used in lactase trials, with directions to take one more if needed
- The lowest cost per 9,000 units of our picks, in individually sealed pouches that are easy to carry
- Plain inactive ingredients, with no sweeteners or sugar alcohols
- The box says the caplets are "for the prevention of" gas, bloating and diarrhea and promises "NO DISCOMFORT", more than the trials show
- "Fast Act" is a name, not a measured speed; we found no published data on how fast it works
- No independent testing we could confirm, and no trial of the current formula
Natural Factors Lactase Enzyme 9000 FCC (60 capsules)
Best for: Reading exactly what is in the capsule
The most complete label here, with the enzyme's source named, at a low cost per dose. The capsule is beef gelatin.
- The most complete label here: 9,000 FCC units, the enzyme's source (Aspergillus oryzae mold) and a definition of the units
- Free of dairy, gluten, wheat, soy and sweeteners, per the brand
- A low cost per 9,000 units
- The capsule is made from beef gelatin, so it is not vegetarian, and the brand says it is not kosher or halal certified
- Its web copy says the enzyme "effectively allows" people to enjoy dairy without discomfort, stronger than its own label's "may"
- The label's third-party seal could not be confirmed with the certifier
Enzymedica DairyAssist (30 capsules)
Best for: Vegans and people avoiding common allergens
A vegan 9,500-unit capsule free of the common allergens. The added protease has no trial support for dairy symptoms.
- 9,500 units of lactase in one vegan capsule, the only pick here labeled vegan, and kosher per its label
- Free of gluten, dairy, soy and artificial colors and flavors
- Lists the activity of both enzymes, even though they sit in a named blend
- Adds a protein-digesting enzyme (protease); we found no trial showing it helps with dairy symptoms
- The brand page promises enzymes that "completely digest dairy" and calls Enzymedica the "#1 selling enzyme brand"
- The label was recently reformulated (older labels list 5,000 units), so check the bottle you receive
Lactaid Fast Act Chewables, Vanilla Twist (60 chewables)
Best for: People who prefer not to swallow pills
The caplet's dose in a vanilla chewable. It contains mannitol, a sugar alcohol, and sucralose.
- The same 9,000 FCC dose as the caplets in a vanilla chewable, useful if you dislike swallowing pills
- Single-serve pouches, with directions to take a second tablet if needed
- Labeled for ages 4 and up
- Sweetened with mannitol, a sugar alcohol that can cause gas or loose stools in larger amounts, plus sucralose and artificial flavor; the label does not give the mannitol amount
- The same "prevention" and "NO DISCOMFORT" box claims as the caplets
- Costs more per dose than the caplets
Source Naturals Lactase Digest (180 capsules)
Best for: Matching the dose to small or large servings
3,000-unit capsules let you dose by the meal. It contains wheat and costs more per dose.
- 3,000 units per capsule lets you match the dose to a small or large serving of dairy, up to 9,000 units
- Vegetarian capsule, and the label names the enzyme's source (Aspergillus oryzae)
- Modest label claims
- The label says it contains wheat, so skip it if you avoid gluten or wheat
- One capsule is below the 4,500 units the EU requires for a lactase digestion claim, so most meals need two or three
- One of the higher costs per 9,000 units here
Nature's Way Lactose Defense (100 capsules)
Best for: Scaling the dose, dairy and soy free
Scalable 3,450-unit capsules with no dairy or soy. The highest cost per dose here.
- 1 to 3 capsules gives 3,450 to 10,350 units, so you can scale the dose to the meal
- Free of dairy, soy and artificial colors and flavors, per the label
- Simple ingredients: lactase, cellulose, a gelatin capsule and magnesium stearate
- The highest cost per 9,000 units of our picks
- One capsule is below the EU's 4,500-unit minimum for a digestion claim, and the current label makes no gluten-free statement
- Calls itself a "quick-dissolving capsule" with no data shown
The full lineup, side by side
Amounts come from each product's Supplement Facts panel on the brand's website or in the NIH Dietary Supplement Label Database, read November 10, 2026. FCC units and ALU (acid lactase units) measure the same thing.
| Product | Lactase per dairy serving | Form | Worth knowing | Testing | Cost tier | Score |
|---|---|---|---|---|---|---|
| #1 Lactaid Fast Act | 9,000 FCC (1 caplet) | Caplet | No sweeteners; kosher per brand | None confirmed | $ | 4.2 |
| #2 Natural Factors | 9,000 FCC (1 capsule) | Gelatin capsule | Free of dairy, gluten, soy | Unconfirmed seal | $ | 4.1 |
| #3 Enzymedica DairyAssist | 9,500 units (1 capsule) | Vegan capsule | Vegan; adds protease | None confirmed | $$ | 4.0 |
| #4 Lactaid Chewables | 9,000 FCC (1 chewable) | Chewable | Mannitol, sucralose | None confirmed | $$ | 3.8 |
| #5 Source Naturals | 3,000 to 9,000 units (1 to 3) | Vegetarian capsule | Contains wheat | None confirmed | $$$ | 3.8 |
| #6 Nature's Way | 3,450 to 10,350 units (1 to 3) | Gelatin capsule | No dairy or soy | Unconfirmed claim | $$$ | 3.8 |
Cost tiers compare the cost per 9,000 lactase units of the products on this page when we reviewed them ($ lower, $$ mid-range, $$$ higher). Prices change often, so check the current price on Amazon. Scores are rounded: Lactaid Fast Act scores 4.150 and Natural Factors 4.125, and among the three at 3.8, the chewables score 3.825, Source Naturals 3.800 and Nature's Way 3.775.
How to choose, and what to check first
Read the units, not the milligrams. Lactase strength is measured in FCC units (also printed as ALU). A label that gives only milligrams does not tell you the strength. One tablet with 9,000 units covers a typical dairy serving in the trials; a larger meal may need a second tablet, as several labels allow.
Check the inactive ingredients. Chewables often use sugar alcohols such as mannitol, which can cause gas or loose stools in larger amounts. Look for wheat if you avoid gluten, and gelatin if you avoid animal products.
Take it with the first bite. If the meal goes on for a while, labels suggest another dose after 30 to 45 minutes. For milk you drink, lactose-free milk does the same job without a pill. If lactose is only one of several foods that bother you, see our low-FODMAP guide, and for broader enzyme blends see our digestive enzyme ranking.
- Get the diagnosis right. Bloating after dairy can also come from celiac disease, IBS or other conditions. See a doctor for new or severe symptoms, weight loss, blood in your stool or diarrhea that wakes you at night.
- Milk allergy and galactosemia. Lactase does not help either one. People with galactosemia must avoid milk sugar entirely.
- Children. Follow the age on the label (Lactaid says 4 and up, Nature's Way 12 and up), and ask a pediatrician before cutting dairy from a child's diet.
Frequently asked questions
What is the best lactase supplement?
Lactaid Fast Act caplets ranked first: 9,000 FCC units in one caplet, plain inactive ingredients and the lowest cost per dose of our picks. Natural Factors has the most complete label, and Enzymedica DairyAssist is the vegan pick.
How much lactase do I need?
Trials used roughly 3,000 to 9,900 FCC units with a dairy meal, and the EU allows a lactose digestion claim only at 4,500 FCC units or more per meal. Many people do well with one 9,000-unit tablet; a large dairy meal may need a second, as several labels allow.
When should I take a lactase pill?
With the first bite or sip of dairy, because the enzyme works in the gut while the lactose is there. If the meal lasts longer than 30 to 45 minutes, labels suggest another dose.
Is Lactaid better than store or generic lactase?
The active enzyme is the same kind, so the dose in FCC units, the inactive ingredients and the cost matter more than the name. No trial we found tested a current lactase product, Lactaid included.
Are lactase supplements safe?
Short trials reported few side effects, and allergic reactions to lactase tablets are rare but have been reported. Chewables may contain sugar alcohols that can cause gas. Lactase does not help a milk allergy and is not a safe workaround for galactosemia.
The bottom line
Lactase pills help many people digest dairy, though results vary and no trial tested a product on this list. Choose one that gives 4,500 to 9,000 or more FCC units per serving and take it with the first bite. Lactaid Fast Act caplets offer that dose with plain ingredients at the lowest cost per dose of our picks, Natural Factors has the most complete label, and Enzymedica DairyAssist suits vegans. Skip the chewables if sugar alcohols bother you, and the Source Naturals capsules if you avoid wheat.