A low blood sugar, also called hypoglycaemia or a "hypo", is where the level of sugar (glucose) in your blood drops too low.
It mainly affects people with diabetes, especially if you take insulin.
A low blood sugar can be dangerous if it's not treated promptly, but you can usually treat it easily yourself.
A low blood sugar causes different symptoms for everybody. You'll learn how it makes you feel if you keep getting it, although your symptoms may change over time.
Early signs of a low blood sugar include:
feeling hungry sweating tingling lips feeling shaky or trembling dizziness feeling tired a fast or pounding heartbeat (palpitations) becoming easily irritated, tearful, stroppy or moody turning pale
If not treated, you may then get other symptoms, such as:
weakness blurred vision difficulty concentrating confusion unusual behaviour, slurred speech or clumsiness (like being drunk) feeling sleepy fits (seizures) collapsing or passing out
Hypos can also occur while sleeping, which may wake you up during the night or cause headaches, tiredness or damp sheets (from sweat) in the morning.
If you have a device to check your blood sugar level, a reading of less than 4mmol/L is too low and should be treated.