Hyperemesis Gravidarum: A Complete UK Guide

This complete UK guide explains what you need to know, when to seek help, and how to access the right care. Written by Nub Hub UK for expectant parents navigating pregnancy.

What is hyperemesis gravidarum?

Hyperemesis gravidarum, often called HG, is a severe form of pregnancy nausea and vomiting that goes far beyond typical morning sickness. Unlike ordinary pregnancy nausea, HG involves persistent, relentless vomiting that prevents you from keeping food or fluids down, leading to dehydration, weight loss, and nutritional deficiency. It affects roughly one to three percent of pregnancies in the UK and typically begins between weeks four and ten, peaking around weeks nine to thirteen before gradually easing for most women by sixteen to twenty weeks, though some suffer throughout.

HG versus normal morning sickness

Normal morning sickness, medically termed nausea and vomiting of pregnancy, involves nausea and occasional vomiting but allows you to maintain adequate hydration and nutrition. HG is distinguished by vomiting more than three or four times a day, losing five percent or more of your pre-pregnancy body weight, producing dark or no urine due to dehydration, and feeling dizzy, faint, or confused. If you cannot keep any fluids down for twenty-four hours, seek urgent medical help.

What causes HG?

The exact cause is not fully understood, but it is linked to rising levels of human chorionic gonadotropin, the pregnancy hormone, along with oestrogen and thyroid hormones. Women carrying multiples, those with a history of HG in previous pregnancies, and those with a personal or family history of motion sickness or migraine are at higher risk. There is also a genetic component, and HG tends to recur in subsequent pregnancies.

Diagnosis in the UK

Your GP or midwife will assess your symptoms, check your weight, and test your urine for ketones, which indicate your body is breaking down fat for energy because you are not eating enough. Blood tests may check for dehydration, electrolyte imbalance, and thyroid function. In severe cases you may be referred to your local hospital maternity assessment unit for intravenous fluids. Diagnosis is clinical, based on the severity and impact of your symptoms rather than a single test.

Living with HG

HG can be physically and emotionally devastating. Many women with HG struggle to work, care for family, or leave the house. The condition is often misunderstood as exaggerated morning sickness, which adds to the isolation. Seek support from charities such as Pregnancy Sickness Support, which offers peer support and a helpline. Tell your employer early, as you may need time off or adjustments. Rest, accept help, and do not let anyone dismiss your symptoms as normal.

Treatment overview

Treatment ranges from lifestyle adjustments and oral anti-sickness medication for milder cases to hospital admission for intravenous fluids and stronger antiemetics in severe HG. Combining medications is common when one alone does not work. In the most resistant cases, treatment with steroids or enteral feeding may be considered. Your care plan should be tailored to you, and you should never feel you are making a fuss by asking for help.

Long-term outlook and emotional support

Nub Hub UK provides evidence-based pregnancy information for UK families. Always consult your healthcare team for personalised advice.