Sleep Regression or Teething? How to Tell What's Really Wrecking Your Baby's Sleep

It's 3am, your baby is awake again, and you're running through the list in your head. Is this teething? Is it a sleep regression? Are they coming down with something? When sleep suddenly falls apart, working out why feels urgent — because you assume the fix depends on the cause.

Here's the honest starting point: teething and sleep regressions genuinely can look alike from the outside. Both cause more night waking, harder settling, and a generally unsettled baby. And to make it harder, they can overlap — a baby can absolutely be teething and going through a developmental leap at the same time. Real life doesn't hand you tidy, single explanations.

But they do tend to behave differently, and once you know the signatures, you can usually make a reasonable judgement. In this guide we'll lay out a clear comparison, be straight with you about what teething does and doesn't cause, walk through the regression patterns by age, and give you a calm decision flow so you know what to actually do — regardless of which one it is.

No table is a diagnosis, and your baby won't read the rulebook — but these are the patterns we see most often. Use it as a lean, not a label.

Feature	Sleep regression	Teething
Onset speed	Often builds over a few days; tied to a developmental phase	Tends to flare quickly, around the time a tooth is moving or erupting
Duration	Typically 2–6 weeks; longer and more sustained	Discomfort concentrated in roughly the 3–5 days around a tooth breaking through
Daytime symptoms	New skills practised in the cot (rolling, standing, babbling), clinginess, appetite changes	Drooling, gum-rubbing, chewing everything, flushed cheek, general grizzliness
Feeding changes	Distracted feeding or appetite shifts linked to the developmental stage	May refuse the breast/bottle if sucking hurts sore gums; wants to gnaw instead
What helps	Consistent settling, protecting sleep pressure, riding it out, keeping habits steady	Comfort, something safe to chew, and appropriate pain relief if genuinely needed

The single most useful line in that table is duration. Teething discomfort is short and sharp; a regression is a longer haul. If your baby has been waking badly for two solid weeks, teething alone is an unlikely explanation — which brings us to an honest word about teething.

Teething gets blamed for an enormous amount of disrupted sleep — and often unfairly. So let's be straight, drawing on what the NHS actually says.

According to the NHS, teething symptoms — sore, tender gums, extra dribbling, a flushed cheek, and general fretfulness — tend to be concentrated in the few days around a tooth actually breaking through the gum. In our experience with families, that usually means roughly a 3 to 5 day window of genuine discomfort per tooth, not weeks on end.

So here's our house view, said kindly: weeks of consistently broken sleep is rarely teething alone. A tooth doesn't stay actively erupting for a fortnight. If you've been putting a month of 4am wake-ups down to teething, it's worth gently questioning whether something else — a regression, a habit that's crept in, or a change in routine — is really the driver. This isn't to dismiss teething, which is genuinely uncomfortable; it's just that it's a short-lived cause, and long-running sleep problems usually have a different root.

It's also worth knowing what teething does not reliably cause. The NHS is clear that a high fever, diarrhoea, and vomiting are not typical symptoms of teething and shouldn't be dismissed as "just teething" — if your baby has these, they should be checked over as they may be unwell for another reason. For the full picture of how teething interacts with sleep, our dedicated guide on teething and sleep goes further.

Sleep regressions aren't random — they cluster around predictable developmental stages, and knowing the typical windows helps you recognise one when it lands. These are the ages we see most, though your baby's timing may vary.

• Around 4 months. The big one, and the only truly permanent change. Your baby's sleep matures into more adult-like cycles and they start surfacing between them, leading to more frequent night waking and shorter naps. See our 4-month sleep regression guide for the full explanation.
• Around 8 to 10 months. Driven by a burst of physical and cognitive development — crawling, pulling to stand, and often a peak in separation anxiety. Babies practise their new skills in the cot at 2am. Our 8-month sleep regression guide covers it.
• Around 12 months. Often tangled up with walking, a possible nap transition, and language leaps. More on this in our 12-month sleep regression guide.
• Around 18 months. A toddler classic — growing independence, testing boundaries, big feelings, and separation anxiety flaring again. Our 18-month sleep regression guide unpacks it.
• Around 24 months. Two-year-olds contend with imagination and new fears, further language development, and sometimes potty training or a new sibling. It's a genuine wobble even if it's less talked about.

If your baby's sleep disruption lines up with one of these windows and comes with new daytime skills or clinginess, a regression is a strong candidate. Teething, by contrast, can strike at almost any age from around 6 months and isn't tied to these developmental clusters.

There's a third culprit that often gets overlooked in the teething-versus-regression debate, and it's an important one: your baby might simply be unwell. Coughs, colds, ear infections, tummy bugs, and the general parade of childhood illnesses all wreck sleep, and a baby who "suddenly" stops sleeping may be brewing something.

Illness is worth keeping firmly in mind because — unlike teething and regressions — it sometimes needs a medical response, not just patience and comfort. A blocked nose makes lying flat and feeding miserable; an ear infection is often worse when lying down, which is why it hits night sleep hard; a temperature disrupts sleep all on its own.

The clues that point to illness over teething or a regression include a genuine fever, a runny or blocked nose, a cough, going off feeds significantly, unusual lethargy, pulling or batting at an ear, or a baby who just seems "not themselves" beyond the usual grizzliness. Our guide on illness and sleep walks through how to support a poorly baby's sleep and when disrupted sleep is a sign to seek advice.

The practical takeaway: before you settle on "teething" or "regression," do a quick sweep for signs of illness. If they're there, that takes priority.

Here's the part that matters most, and it's genuinely freeing: you usually don't need a perfect diagnosis to respond well. The right first move is broadly the same whether it's teething, a regression, or the early stage of a bug. Here's the flow we'd suggest.

Step 1 — Comfort first, for two to three nights. When sleep falls apart, respond with reassurance and comfort. Go to your baby, soothe them, and meet them where they are. You are not "creating bad habits" by comforting a distressed or uncomfortable baby over a few tough nights — you're being responsive, which is exactly right in the short term.

Step 2 — Reassess after those few nights. If things are settling and it was clearly a short flare, it was likely teething or a passing niggle. If the disruption is dragging on past that initial window, lean towards a regression or a habit that's crept in, and shift your focus back towards your usual, consistent settling approach.

Step 3 — Don't abandon good habits for either cause. This is the big one. It's tempting, in the fog of a bad patch, to introduce something new to survive — a fresh sleep prop, a return to feeding to sleep, hours of rocking. Comforting your baby through a rough stretch is fine; permanently rewriting their sleep because of a temporary cause is what tends to leave you with a longer-term problem once the tooth is through or the regression passes. Comfort generously, but keep the underlying framework steady.

Step 4 — Check for illness throughout. If at any point signs of genuine illness appear, that changes the picture and may need a medical response rather than a sleep response.

If your baby is in genuine teething pain and comfort measures aren't enough, appropriate pain relief can help. Infant paracetamol and infant ibuprofen are available for babies, but the NHS is clear that they must be given strictly according to the age and weight guidance on the packaging — dosing isn't something to guess at. If you're at all unsure whether pain relief is appropriate, or which and how much, ask your pharmacist or GP first. A pharmacist is a free, expert, and very accessible source of advice on exactly this.

Alongside the sleep question, the usual safe-sleep principles never bend, no matter how rough the night. Always place your baby on their back to sleep on a flat, firm surface with a clear cot — no pillows, wedges, weighted products, or bulky bedding, all of which are unsafe. Keep the room at a comfortable 16–20°C. And critically, never fall asleep with your baby on a sofa or armchair — the Lullaby Trust warns this carries a risk of SIDS up to 50 times higher than a safe sleep space. On exhausting teething nights the sofa is a real temptation; please resist it, and if you might drift off, move to a bed set up according to safer co-sleeping guidance.

Finally, the honest boundary: this is sleep support, not medical advice. If your baby has a high fever, seems genuinely unwell, is very lethargic, is refusing feeds, or you're simply worried, contact your GP or call 111 — and trust your instinct, because you know your baby best. For a plan that helps you tell these causes apart and respond calmly next time, our guide to sleep consultant costs in the UK lays out the options, and our £97 baby sleep course covers regressions, teething, and illness in one place. You're doing brilliantly through a genuinely hard patch.