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Written by The HG Collective · Reviewed by HG Clinicians Expert Panel · Last reviewed: July 2026

Pregnancy sickness and HG: symptoms and diagnosis

Nausea and vomiting in pregnancy are common and can vary considerably in severity. Symptoms usually begin early in pregnancy and, for most people, improve by 20 weeks. Hyperemesis gravidarum (HG) is the severe end of this spectrum. It can prevent someone from eating and drinking normally, severely restrict everyday life and lead to dehydration, weight loss and nutritional problems.

You do not have to be vomiting to have HG. Under the internationally agreed Windsor Definition, severe nausea alone can meet the definition when it prevents normal eating or drinking and strongly limits daily activities.

You also do not need to wait until you are dehydrated, losing weight or unable to keep anything down before asking for help. Symptoms that do not meet every criterion for HG may still need treatment.

How does pregnancy sickness differ from HG?

Pregnancy sickness is common. It often begins between 4 and 7 weeks of pregnancy, is usually worst at around 9 weeks and improves by 20 weeks for most people.

HG is more severe. The Windsor Definition describes HG as:

  • symptoms beginning before 16 weeks of pregnancy;
  • severe nausea and/or vomiting;
  • being unable to eat and/or drink normally; and
  • symptoms that strongly limit daily activities.

Signs of dehydration can support the diagnosis, but they are not required. Neither is a particular amount of vomiting. Severe nausea without frequent vomiting can still be HG.

“Beginning before 16 weeks” refers to when the symptoms start. HG can continue beyond 16 or 20 weeks and, for some people, lasts until birth. If nausea or vomiting starts for the first time at or after 16 weeks, your healthcare team should consider other possible causes.

What signs and symptoms should I look out for?

HG does not look exactly the same for everyone. Possible signs include:

  • severe or prolonged nausea, even if you are not vomiting;
  • repeated vomiting or retching;
  • difficulty eating or drinking normally;
  • being unable to keep down fluids, food or medication;
  • losing weight;
  • excessive saliva or needing to spit frequently;
  • feeling very weak, exhausted, dizzy or lightheaded;
  • passing much less urine than usual, or urine that is dark yellow and strong-smelling;
  • a dry mouth or lips, intense thirst or other signs of dehydration; and
  • symptoms that make ordinary activities—such as washing, working, caring for others or leaving bed—very difficult or impossible.

You do not need to have every symptom on this list, and vomiting frequency alone does not show how unwell you are.

When should I ask for help?

Contact your GP, midwife, maternity unit or early pregnancy service promptly if nausea or vomiting is making it difficult to eat, drink, take medication or manage normal daily activities. Ask for help if you are losing weight or have signs of dehydration, including dizziness, intense thirst, a dry mouth, very dark urine or passing much less urine than usual.

Seek urgent medical advice if you cannot keep fluids or essential medication down, are passing very little or no urine, feel faint or seriously unwell, or have another health condition—such as diabetes or epilepsy—that could become unsafe when you cannot eat, drink or take medication normally.

You do not need to wait for symptoms to become an emergency. You also do not need to wait for a urine test to show ketones before treatment can be offered.

How is HG diagnosed?

There is no single blood test, urine test or scan that proves whether someone has HG. Diagnosis is based on your symptoms and a clinical assessment, using the Windsor Definition and ruling out other possible causes.

Your healthcare professional may ask about:

  • when your symptoms began;
  • the severity of nausea, vomiting and retching;
  • what you can eat and drink, and whether you can keep medication down;
  • weight loss and signs of dehydration;
  • the effect on daily life and emotional wellbeing;
  • previous pregnancies with HG; and
  • other symptoms or medical conditions that could suggest a different or additional cause.

They may check your weight, pulse, blood pressure, temperature and hydration. Urine and blood tests may be used to look for complications or other conditions, and an ultrasound may be offered when clinically indicated—for example, to confirm the pregnancy or check for multiple pregnancy. These investigations support safe care; they are not a test of whether your symptoms are real.

What about urine ketones?

A urine sample can still be useful—for example, to look for signs of a urinary tract infection. What has changed is the use of ketones. Current RCOG guidance says ketones in urine do not reliably show dehydration or the severity of HG. They should not be used to diagnose HG, decide how unwell you are, determine whether you need admission or delay treatment.

How is severity measured?

Your team may use a symptom questionnaire to record severity and response to treatment. The Pregnancy-Unique Quantification of Emesis (PUQE) score can help assess mild-to-moderate pregnancy sickness, but it has not been validated for severe HG. The HyperEmesis Level Prediction (HELP) score includes a wider range of symptoms and has been validated across the full spectrum, including severe disease. Neither score replaces clinical judgement or the Windsor Definition.

What happens next—community, day care or hospital?

The right setting depends on your symptoms, hydration, weight loss, other health conditions, whether you can keep down medication and fluids, and how you have responded to treatment.

Community care

If you are able to drink and are not clinically dehydrated, care may begin with your GP, midwife or maternity team. This can include anti-sickness medication, advice about oral fluids and food, and follow-up. Treatment can still be appropriate even if your symptoms are described as mild or moderate.

Ambulatory or day-case care

If community treatment is not enough, or you cannot tolerate oral fluids or medication, you may be offered ambulatory care. This usually means attending hospital for assessment, fluids through a drip, vitamins including thiamine, and anti-sickness medication, then going home the same day if it is safe. Repeat visits may be arranged.

Inpatient care

An overnight hospital stay may be considered if you are clinically dehydrated, have lost more than 5% of your pre-pregnancy weight despite oral treatment, cannot keep down oral medication, have another condition that needs treatment, or remain unwell despite adequate ambulatory care. Admission decisions should be based on the whole clinical picture—not urine ketones alone.

Care is not yet consistent everywhere

Local pathways vary. Some hospitals have dedicated day-case services and others do not. If the care available near you differs from what is described here, that reflects real variation between services—not a failure on your part.

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