Constant hunger: causes of being always hungry and when to check

Hunger is a signal, not a disease, and it varies with how much and when you eat, how active you are, how well you sleep and where you are in your menstrual cycle. A day of heavy exercise or a few nights of poor sleep can make anyone feel hungrier. Appetite that changes in a predictable way, such as before a period, often has a simple explanation.

The NHS lists changes in appetite or food cravings among the common symptoms of premenstrual syndrome and suggests that eating frequent smaller meals every 2 to 3 hours may suit some people better. A symptom diary kept for at least 2 menstrual cycles shows whether hunger follows a monthly pattern.

What makes hunger worth investigating is a new, persistent change that does not fit your circumstances, particularly if it comes with other symptoms. The key one is unintentional weight loss, as the table shows, alongside thirst, passing more urine than usual and tiredness.

Diabetes causes blood glucose to become too high. The NHS says its most common symptoms are feeling thirsty all the time, peeing more than usual, feeling very tired and losing weight without trying. Diabetes UK explains that when there is not enough insulin to move glucose from the blood into the cells, the cells lack the energy they need, which leaves you tired, and that the body may break down fat as an alternative energy source, which can lead to weight loss. Increased hunger is on its list of other symptoms.

Not everyone with type 2 diabetes has symptoms, and the NHS says they may develop gradually. It says to ask for an urgent GP appointment or NHS 111 help if you or your child has any symptoms of diabetes, and a GP appointment if you are at higher risk. Diagnosis is by a blood test that checks blood glucose levels. Type 2 diabetes risk is higher if you are white and over 40, or over 25 and from a South Asian, Chinese, Black African or Black Caribbean background, if a parent or sibling has it, or if you are overweight and not very active.

An overactive thyroid produces too much thyroid hormone, which affects heart rate and body temperature. The NHS lists nervousness, anxiety and irritability, mood swings, difficulty sleeping, feeling tired all the time, sensitivity to heat, muscle weakness, diarrhoea, palpitations, trembling and weight loss, and says weight loss is often despite an increased appetite. A GP can arrange a blood test to check thyroid function. It is about 10 times more common in women than men, and typically happens between 20 and 40 years of age.

Low blood sugar, defined by the NHS as usually below 4mmol/L, causes feeling hungry along with dizziness, anxiety, sweating, shaking and other symptoms. It usually affects people with diabetes who take insulin or some other diabetes medicines and is rare in people without diabetes. The NHS says to see a GP if you do not have diabetes and you get symptoms such as shaking, sweating, a fast heartbeat and feeling confused.

If hunger is new, relentless and out of keeping with your usual pattern, and especially if you have noticed weight loss without trying, thirst, passing urine often or persistent tiredness, make a GP appointment and mention all of these. The NHS says to seek urgent advice if you suspect diabetes. A blood test for glucose and, if indicated, thyroid function is straightforward.

Meanwhile a food and symptom diary helps: when you eat, when hunger starts, any weight change, sleep, medicines and your cycle. If you have diabetes and treatment-related low blood sugar, follow your care team's plan, which the NHS says includes having something to raise blood sugar quickly to hand.