Written by Charlotte Howden · Reviewed by HG Clinicians Expert Panel · Last reviewed: July 2026
Symptoms and Diagnosis
If you're not sure whether what you're experiencing is "normal" pregnancy sickness or something more, here's how to tell the difference — and what happens when you see a doctor or midwife.
How is HG different from normal pregnancy sickness?
Most pregnant people feel some nausea or sickness in early pregnancy — it's common and usually settles between 12 and 16 weeks. HG is different. It's severe nausea and/or vomiting — you don't have to be vomiting to have HG, severe nausea alone can be enough — that stops you eating and drinking normally and strongly limits your daily life, often alongside signs of dehydration.
It starts early, before 16 weeks, and for some people it lasts the whole pregnancy rather than settling by 20 weeks.
What are the signs to look out for?
Signs that this may be HG, not just morning sickness, include:
- Constant nausea, whether or not you're actually being sick
- Vomiting many times a day, not able to keep food or fluids down at all
- Losing weight
- Feeling constantly dizzy, lightheaded, or exhausted
- Signs of dehydration — feeling unusually thirsty, feeling "dry," passing much less urine than normal, or urine that's dark yellow or brown
- Symptoms so severe they stop you doing normal daily activities
If any of this sounds like you, it's a good reason to contact your GP, midwife, or maternity unit — you don't need to wait until it feels like an emergency, and you don't need to be vomiting to be taken seriously.
How is HG diagnosed?
There's no single test for HG — it's diagnosed from your symptoms and a clinical assessment against the internationally agreed Windsor Definition, not from one specific blood test or scan. Your healthcare team will ask about how often you're vomiting and whether nausea alone is severe, whether you can keep anything down, how it's affecting your day-to-day life, and whether you're showing signs of dehydration. They may also do some tests, mainly to check for other things that can cause similar symptoms (like a urine infection or thyroid problems), and to see how dehydration is affecting your body — not to "prove" you have HG.
One outdated practice worth knowing about:you may have heard that a urine test for "ketones" is used to check how severe HG is, or even to diagnose it. Current evidence and UK guidance (updated 2024) say this is no longer considered reliable, and a biochemical marker like this was never required by the Windsor Definition in the first place — so don't be concerned if your team doesn't use it, or reassured if they do.
What happens next — community, day care, or hospital?
Most people with mild-to-moderate symptoms are looked after by their GP or midwife, with anti-sickness medication and practical advice. Many hospitals also offer ambulatory (day-case) care — you go in for a few hours for fluids through a drip and anti-sickness medication, then go home the same day, and can come back if things get bad again. Hospital admission and an overnight stay is used for more severe cases, or if outpatient treatment hasn't worked.
This varies by trust.Not every hospital offers the same pathway, and care can differ quite a bit depending on where you live — some units have day-case ambulatory care, some don't; some screen for HG at your booking appointment, most don't yet. If something you've read here doesn't match what you're offered locally, that's a real gap in national consistency, not something wrong with you — and it's exactly the kind of variation we're working to close.