If milk or ice cream leaves your tummy rumbling and sore, then diarrhoea, it may be lactose intolerance. The UK National Health Service (NHS) says symptoms can start a few minutes, or a few hours, after food or drink containing lactose. The most common cause is the body not making enough lactase, the enzyme that digests lactose; it can also follow other conditions such as coeliac disease, inflammatory bowel disease or a bowel infection. Here is the NHS guidance on hidden lactose, when to see a GP or call 999, tests and treatment.
1. Symptoms minutes to hours after lactose — tummy pain, bloating, farting, rumbling, diarrhoea or constipation, feeling or being sick.
2. See a GP if bowel changes, blood in poo or bloating last 3 weeks, or you lose weight without trying.
3. Tests: an elimination diet, blood tests, a hydrogen breath test — don’t cut foods out without advice.
Symptoms — NHS
| Type | What the NHS says | Worth noting (ours) |
|---|---|---|
| When | A few minutes, or a few hours, after food or drink containing lactose | — |
| Common | Tummy pain or discomfort, bloating, farting, tummy rumbling, diarrhoea or constipation, feeling or being sick | — |
| Beyond the gut | Headaches, tiredness, joint or muscle pain | — |
| Not an allergy | A food allergy can cause difficulty breathing, itchy skin and swelling of the lips, face and eyes, and can be life threatening | See the 999 table below |
Foods that contain lactose — NHS
| Type | What the NHS says | Worth noting (ours) |
|---|---|---|
| Animal milk | Milk from cows, goats and sheep | — |
| Dairy | Milk, butter, cheese, cream, yoghurt, ice cream | Lattes, milk tea and cream soups too (ours) |
| Processed foods | Muesli and cereals with chocolate; bread, crackers, cakes, biscuits and pastry | Look for lactose, milk powder or whey on labels (ours) |
| Sauces, drinks | Sauces and salad dressings; diet and protein shakes | Many protein powders are whey-based (ours) |
When to get help — NHS
Some symptoms are common, but get help if they keep happening or don’t go away. See a GP if you have symptoms of lactose intolerance and:
- they keep coming back and often happen after eating
- your poo has changed — looser, more often, or constipation — for 3 weeks
- you’ve had blood in your poo for 3 weeks
- you’ve had tummy bloating and discomfort for 3 weeks
- you’ve been losing weight without trying
The following are signs of a serious allergic reaction (anaphylaxis), not intolerance; the NHS says call 999. Anaphylaxis needs immediate hospital treatment.
| If | NHS advice | Worth noting (ours) |
|---|---|---|
| Lips, mouth, throat or tongue suddenly swollen | Call 999 | In Korea, 119 (ours) |
| Breathing very fast or struggling to breathe (wheezy, choking, gasping) | 999 | — |
| Throat feels tight or struggling to swallow | 999 | — |
| Skin, tongue or lips blue, grey or pale | 999 | On black or brown skin, easier to see on palms or soles |
| Suddenly very confused, drowsy or dizzy; someone faints and cannot be woken | 999 | — |
| A child is limp, floppy or not responding normally | 999 | A swollen, raised or itchy rash may also appear — signs of anaphylaxis |
Tests — NHS
| Type | What the NHS says | Worth noting (ours) |
|---|---|---|
| Elimination diet | Stop foods containing lactose to see if symptoms improve | Done when a GP suggests it |
| Blood tests | A GP may arrange them | — |
| Hydrogen breath test | Measures hydrogen gas in your breath to see how well you digest lactose | — |
| Gastroscopy | If severe and not improving: a thin tube into the stomach; a small sample of small-intestine cells may be taken. Painkillers or a sedative may be given | — |
Treatment — NHS
| Type | What the NHS says | Worth noting (ours) |
|---|---|---|
| Reduce or avoid | For most people, reducing or avoiding lactose foods prevents symptoms | The page gives no amount |
| Caution | Don’t cut foods out of your or your child’s diet without a GP or dietitian | Cutting dairy can lower calcium intake (ours) |
| Lactase supplement | Taken before lactose food or drink, may reduce or prevent symptoms for some | — |
| Underlying cause | If caused by a condition such as coeliac disease, treating it should help | — |
Causes — NHS
The most common cause is the body not making enough lactase. It can start at any age, and can also be caused by inflammatory bowel disease or coeliac disease, bowel infections, bowel surgery or an injury to the bowel. Some premature babies can’t digest lactose because the bowel hasn’t developed enough, which usually gets better as they grow; making no lactase at all is very rare.
Gluten damaging the small intestine is covered in coeliac disease; other intolerances in food intolerance.
Checklist
- ☐ Symptoms minutes to hours after dairy?
- ☐ Check labels for hidden lactose (cereals, bread, sauces, protein shakes)
- ☐ Bowel changes, blood or bloating for 3 weeks, or weight loss: see a GP
- ☐ Swelling of lips or throat, breathing trouble: allergy — emergency
- ☐ Ask a GP or dietitian before cutting foods; lactase before eating
Questions that remain
Do I have to stop milk completely?
The NHS says reducing or avoiding lactose prevents symptoms for most people, but not to cut foods out without advice. The page gives no amount you can safely have.
Is lactose intolerance the same as a milk allergy?
No. The NHS separates food intolerance from food allergy, which can cause breathing difficulty and swelling and can be life threatening.
Sources
- NHS — Lactose intolerance — source (page shows: reviewed 8 July 2026, next review due 8 July 2029; checked 5 November 2026). Symptoms and timing, foods with lactose, allergy vs intolerance, 5 GP criteria (3 weeks), 7 999 criteria, 4 tests, treatment (reduce, lactase, underlying cause), causes.
- Not read. Allergy UK label guidance; tolerated amounts; Korean guidance.
- What we added. The “worth noting” column and the Korean care gloss.
Where to check further
- A gastroenterologist — symptoms lasting over 3 weeks.
- A dietitian — keeping up calcium while cutting dairy.
Written on 5 November 2026. The content is from the NHS; the glosses are ours.
