HG is not just bad morning sickness

Hyperemesis gravidarum is a serious medical condition that requires treatment. If you cannot keep any food or fluid down, are losing weight, or feel dizzy and weak, contact your GP, midwife or maternity unit today. Do not wait and hope it passes. Dehydration in pregnancy needs prompt treatment.

This information is for general guidance only.

It does not replace advice from your midwife, GP or obstetric team. Read more about our approach.

Hyperemesis gravidarum: severe sickness in pregnancy

What is hyperemesis gravidarum?

Hyperemesis gravidarum (HG) means extreme nausea and vomiting in pregnancy. It is significantly more severe than ordinary morning sickness and can be debilitating. It is estimated to affect around 1 to 3 in every 100 pregnant women in the UK, though under-reporting means the true figure may be higher.

Unlike normal pregnancy nausea, which typically eases by 12 to 16 weeks, HG can persist throughout the entire pregnancy for some women.

Morning sickness versus hyperemesis gravidarum

Normal morning sickness

  • Nausea with some vomiting
  • Usually manageable with rest and dietary changes
  • Typically improves by 12-16 weeks
  • Able to keep some food and fluid down
  • Does not usually cause weight loss
  • Does not usually require medical treatment

Hyperemesis gravidarum

  • Prolonged, severe nausea and vomiting — often 10+ times daily
  • Unable to keep food or fluid down for extended periods
  • Often continues beyond 16-20 weeks, sometimes entire pregnancy
  • Significant weight loss (5% or more of pre-pregnancy weight)
  • Dehydration: dark urine, dizziness, weakness, rapid heart rate
  • Major impact on work, daily life and self-care
  • Requires medical treatment, often hospital admission

Symptoms of HG

  • Severe and persistent nausea (often constant, not just morning)
  • Vomiting many times a day, unable to keep fluids down
  • Dehydration: dark or no urine output, dry mouth, dizziness
  • Significant weight loss
  • Extreme fatigue and weakness
  • Difficulty speaking, standing or performing daily tasks
  • Sensitivity to smells or light (photophobia)
  • Muscle weakness from electrolyte imbalance
  • Low mood, anxiety and, in some cases, depression

Causes

The exact cause of HG is not fully understood. Strong evidence links it to elevated levels of hCG (the pregnancy hormone) in early pregnancy, which may explain why it is more common in:

  • Multiple pregnancies (higher hCG levels)
  • Molar pregnancies
  • First pregnancies

Genetic factors matter too. HG runs in families. If your mother or sister had HG, you are more likely to experience it. If you had HG in a previous pregnancy, you are very likely to have it again.

HG is not caused by anxiety, weakness, or anything you have done. It is a physical condition with a physiological cause.

Getting help, without delay

Contact your GP, midwife or maternity unit if you:

  • Cannot keep any fluids down for 24 hours or more
  • Have not urinated, or your urine is very dark
  • Feel dizzy, faint or cannot stand
  • Have lost weight
  • Are unable to carry out basic daily activities
  • Feel you cannot cope

What to say.Use the words “hyperemesis gravidarum” so you are taken seriously and assessed appropriately. You do not have to push through this alone.

Diagnosis and assessment

There is no single test for HG. Diagnosis is based on your symptoms. Your GP or hospital will check:

  • Urine for ketones (a sign of starvation or dehydration)
  • Blood tests: electrolytes, full blood count, thyroid function
  • Weight and vital signs
  • An ultrasound may be offered to confirm a viable pregnancy and check for multiple pregnancy

Treatment

Community treatment (GP or midwife)

Anti-sickness medication:

  • Cyclizine — first-line, safe in pregnancy
  • Prochlorperazine (Stemetil) — tablet or buccal (useful if you cannot swallow)
  • Promethazine — useful for sleep
  • Ondansetron — increasingly used in the UK for HG that is not responding to other medications; safety confirmed by BUMPS
  • Vitamin B6 (pyridoxine) — may help mild to moderate nausea
  • Ginger — some evidence of mild benefit
  • Thiamine (vitamin B1) supplementation — important in HG to prevent Wernicke's encephalopathy

Combining medications that work in different ways is often more effective than increasing the dose of one.

Hospital treatment (when unable to keep fluids down)

  • IV fluids (drip) for rehydration, often bringing rapid relief
  • IV anti-sickness medication, faster-acting than tablets
  • IV thiamine to prevent neurological complications
  • Monitoring of electrolytes and correction as needed
  • Some women require multiple admissions
  • TPN (total parenteral nutrition) in very severe cases — rare

Hospital admission is not a failure. It is appropriate treatment.

Practical management at home

  • Rest as much as possible — fatigue worsens nausea.
  • Eat little and often: bland, dry foods (crackers, plain rice, toast).
  • Cold foods are often tolerated better than hot (less smell).
  • Ice chips, frozen fruit or ice lollies for fluid intake.
  • Avoid triggers: strong smells, cooking odours, fatty foods.
  • Separate eating from drinking, sipping fluids between meals.
  • Small sips of cold water, diluted squash, flat cola or Dioralyte.
  • Keep food preparation out of sight if smells trigger nausea.

Emotional and psychological impact

HG can be traumatic. Being severely ill during what is supposed to be a happy time causes grief, guilt and loss of control.

Common experiences

  • Feeling unable to bond with the pregnancy due to suffering
  • Guilt about not enjoying pregnancy
  • Anxiety about HG recurring in future pregnancies
  • Relationship strain and practical difficulties
  • Depression during and after illness
  • In severe, prolonged cases, some women consider termination. This is a deeply personal decision and you deserve support without judgement if you reach this point.

Support: Pregnancy Sickness Support (pregnancysicknesssupport.org.uk) runs a peer support network, helpline and online resources specifically for HG. They can pair you with someone who has been through it.

After HG

Most women experience significant improvement or complete resolution after delivery, sometimes immediately. Some residual nausea or food aversions may continue postnatally.

If you plan future pregnancies, tell your GP or midwife about your HG history at your booking appointment. Anti-sickness medication can be prescribed early, before symptoms peak. Early treatment significantly improves outcomes and may prevent hospital admission.

Related guides and tools

Common pregnancy symptoms→ Vitamins and supplements in pregnancy→ Mental health support in pregnancy→ Nutrition during pregnancy→

A note from our team

This guide reflects NHS UK, RCOG and Pregnancy Sickness Support guidance on HG. If you are living with HG, please know that what you are experiencing is real, serious, and deserving of treatment. Read more about us.

Frequently asked questions

What is the difference between morning sickness and HG?
Morning sickness is nausea with some vomiting that is usually manageable with rest and dietary changes, and tends to improve by 12 to 16 weeks. HG is prolonged, severe and debilitating. It typically involves vomiting many times a day, inability to keep food or fluid down, significant weight loss, dehydration, and a real impact on your ability to function. HG requires medical treatment, sometimes hospital admission.
Is it safe to take anti-sickness medication in pregnancy?
Yes, for the medications used for HG in the UK. Cyclizine, promethazine, prochlorperazine and ondansetron are all used routinely with a strong safety record. The BUMPS (Best Use of Medicines in Pregnancy) website provides evidence-based information on each. The risks of untreated severe vomiting, including dehydration and weight loss, are greater than the small risks of well-established medications.
Will HG harm my baby?
Severe, untreated HG with significant weight loss can occasionally affect baby's growth, which is why prompt treatment matters. With appropriate medical care, most women with HG have healthy babies. Your pregnancy will usually be monitored with extra scans to check growth if HG has been severe or prolonged.
When should I go to hospital for HG?
If you cannot keep any fluids down for 24 hours or more, have not urinated or have very dark urine, feel dizzy or faint, have lost weight, or feel unable to cope. Do not wait and hope it passes. Dehydration in pregnancy needs prompt treatment, often with IV fluids. Hospital admission is not a failure, it is the appropriate treatment for severe HG.
Will I get HG in future pregnancies?
If you have had HG before, you are very likely to have it again, though the severity can vary. Tell your GP or midwife about your history at your booking appointment in any future pregnancy so anti-sickness medication can be prescribed early, ideally before symptoms peak. Early treatment dramatically improves outcomes.
Can HG cause depression?
Yes. HG is physically and emotionally exhausting and the prolonged suffering, isolation and loss of control frequently lead to anxiety and depression. This is a recognised consequence of a serious illness, not a character failing. If you are struggling emotionally, tell your GP, midwife or the Pregnancy Sickness Support helpline. Mental health support is part of treating HG, not separate from it.
What is the safest anti-sickness medication for pregnancy in the UK?
There is no single “safest”, the right choice depends on how you respond. Cyclizine is usually tried first. Prochlorperazine buccal tablets (Buccastem) are useful if you cannot swallow. Ondansetron is increasingly used in the UK when other medications are not enough, and has a good safety record. Your GP may combine two or three medications working in different ways if needed.