Hyperemesis gravidarum (HG) is more than bad morning sickness. It’s persistent vomiting severe enough to cause weight loss of 5% or more of your pre-pregnancy body weight, dehydration, and the inability to keep down adequate food or fluids. While up to 90% of pregnant people experience some nausea and vomiting, HG affects only about 1% to 3% of pregnancies. If you’re reading this, you’re likely trying to figure out whether what you’re going through has crossed that line.
How HG Differs From Morning Sickness
Normal pregnancy nausea is uncomfortable but manageable. You might feel queasy in the morning, vomit occasionally, and still get through most of your day. With HG, the vomiting is relentless. It can happen many times a day, at any hour, and it doesn’t ease up with the usual remedies like crackers, ginger, or small meals. The nausea often feels constant rather than coming in waves.
The clearest distinguishing feature is what happens to your body as a result. Morning sickness rarely causes weight loss. HG does. If you’ve lost more than 5% of your pre-pregnancy weight (for example, 7 or more pounds if you started at 140), that’s a hallmark sign. Other telling symptoms include dry mouth, dark-colored urine, extreme fatigue, constipation, and feeling unable to carry out normal daily activities. You may also notice you’re producing much more saliva than usual.
A useful way to gauge severity is to think about three things: how many hours per day you feel nauseous, how many times you vomit, and how many times you retch or dry heave. Clinicians use a scoring tool called the PUQE that rates these on a scale of 3 to 15. Scores of 13 to 15 indicate severe nausea and vomiting, and the median score for people hospitalized with HG is 13. You don’t need to calculate a formal score, but if nausea is lasting most of the day and you’re vomiting or retching many times, that picture is consistent with HG rather than typical morning sickness.
When Symptoms Typically Start
HG generally begins in the first trimester, often around weeks 6 to 8 of pregnancy. For many people, it peaks in severity somewhere between weeks 9 and 13. In most cases symptoms gradually improve as the pregnancy progresses, but this isn’t guaranteed. HG can persist well beyond the first trimester, occasionally lasting the entire pregnancy or even into the postpartum period. If your symptoms have been escalating rather than improving by the end of the first trimester, that’s worth flagging to your provider.
What Causes It
A 2023 study published in Nature identified a key biological mechanism. The fetus produces a signaling protein called GDF15, and when levels of this protein rise sharply during pregnancy, it triggers nausea and vomiting in the mother. The severity depends not just on how much GDF15 the fetus makes but on how sensitive the mother is to it. Women who had low baseline levels of GDF15 before pregnancy are more reactive to the sudden increase, making them more vulnerable to HG. Interestingly, women with beta-thalassemia, a blood condition that keeps GDF15 chronically elevated, report very low levels of pregnancy nausea, likely because their bodies are already accustomed to the hormone.
This means HG is not caused by anxiety, a weak stomach, or a lack of willpower. It has a measurable biological basis rooted in how your body responds to signals from the placenta and fetus.
Signs of Dehydration to Watch For
One of the biggest risks of HG is dehydration, and it can develop quickly when you’re unable to keep fluids down. The signs to watch for include dark yellow or amber-colored urine, dry skin, weakness, lightheadedness, dizziness, and fainting. Your heart rate may also be noticeably high, especially when you stand up. In one study of women presenting to the emergency department with HG, the average pulse increase upon standing was about 27 beats per minute, nearly double the increase seen after they were rehydrated. That racing or pounding feeling when you get out of bed isn’t just uncomfortable; it reflects real fluid loss.
When dehydration becomes severe, your body starts breaking down fat for energy because you can’t absorb enough calories from food. This produces compounds called ketones, which spill into your urine. Ketones in the urine are one of the markers doctors check when evaluating HG, and their presence confirms your body isn’t getting the nutrition it needs.
How Doctors Evaluate HG
There’s no single definitive test for HG. Diagnosis is largely clinical, meaning your doctor will assess your symptoms, check your weight against your pre-pregnancy baseline, and look for signs of dehydration and nutritional depletion. Lab work typically includes checking urine for ketones and measuring electrolyte levels in your blood, along with kidney function markers. Electrolyte imbalances from prolonged vomiting can cause muscle weakness, cramps, and heart rhythm changes, so these are important to identify.
Your doctor will also want to rule out other conditions that can cause severe vomiting in pregnancy. Thyroid problems sometimes accompany or mimic HG, so thyroid hormone levels are usually checked. Other conditions on the list include gastrointestinal issues and, rarely, molar pregnancy (an abnormal growth in the uterus). This is why a medical evaluation matters even if you’re fairly sure it’s HG. The testing is straightforward, typically involving blood draws and a urine sample, and helps ensure nothing else is going on.
Red Flags That Need Immediate Attention
Certain symptoms mean you should contact your provider right away or go to the emergency room:
- Inability to keep any fluids down for more than 12 hours. At this point dehydration is progressing rapidly.
- Blood in your vomit. This can indicate irritation or tearing of the esophagus from forceful vomiting.
- Lightheadedness, dizziness, or fainting. These suggest significant fluid and electrolyte loss.
- Abdominal pain. Nausea and vomiting are expected with HG, but sharp or localized pain is not and needs evaluation.
- Weight loss exceeding 5 pounds (about 2.3 kilograms). Weighing yourself regularly helps you track this objectively rather than guessing.
What Treatment Looks Like
Mild to moderate cases are sometimes managed at home with prescription anti-nausea medications and dietary adjustments. But when you can’t keep food or fluids down, the first priority is rehydration, usually through intravenous fluids. HG is the most common reason for hospital admission in early pregnancy, and many people with HG need more than one round of treatment.
If you’re admitted, the goal is to restore fluids, correct electrolyte imbalances, and get the vomiting under enough control that you can start tolerating small amounts of liquid and food again. This process can take a day or longer. After discharge, ongoing management often involves a combination of medications, dietary strategies (very small, frequent meals of bland or cold foods), and sometimes home IV fluids for people who continue to struggle with oral intake.
Recovery isn’t always linear. Many people with HG have stretches where symptoms improve followed by flare-ups. The psychological toll is significant as well. Feeling unable to eat, function, or care for yourself or other children during pregnancy is isolating and distressing. If you’re experiencing this, it reflects the severity of the condition, not a personal failing.
Tracking Your Symptoms
If you suspect you have HG but aren’t sure, start keeping a simple daily log. Record how many times you vomit, how many hours you feel nauseous, whether you’re able to keep any food or liquid down, and your weight. Even a few days of this data gives your provider a much clearer picture than trying to recall details from memory at an appointment. A pattern of daily vomiting, escalating weight loss, and an inability to stay hydrated points strongly toward HG and will help you get the right level of care faster.