Reactive Hypoglycaemia

What it is

Reactive hypoglycaemia is a fall in blood sugar within a few hours of eating, usually 2 to 4 hours after a meal. It is the cause of what many people call a mid-morning or mid-afternoon crash: sudden tiredness, hunger and shakiness that lifts as soon as you eat. The problem is one of timing. A meal that raises blood sugar quickly triggers a large release of insulin, which then pulls blood sugar down too far an hour or two later.

Symptoms to look out for

• Shakiness, trembling or weakness
• Sweating, and a fast or pounding heartbeat
• Sudden, strong hunger
• Irritability, anxiety or low mood
• Poor concentration, light-headedness or a foggy head

Symptoms come on a couple of hours after eating and ease when you eat again. They are caused by the low blood sugar itself, and by the adrenaline your body releases in response.

What causes it

The usual trigger is a meal or drink high in sugar or quickly digested carbohydrate, with little protein, fat or fibre to slow it down. People with early insulin resistance are more prone to it, because their insulin response is already less precise. Less often it follows stomach surgery, where food leaves the stomach very quickly. Rarely it points to another condition, so persistent or severe cases need checking.

What you can do

• Food. Diet is the main treatment. Reduce sugary food and drink, and refined carbohydrate such as white bread, rice and pasta. Build meals around a palm-sized portion of protein, fill most of the plate with non-starchy vegetables, and add natural fats. This slows the release of glucose and reduces the insulin spike that causes the later crash.
• How much carbohydrate. Many people find symptoms settle when they eat less carbohydrate overall. Some do well under about 130g a day, others lower still. Treat this as a starting point to test, not a fixed rule.
• Meal pattern. Avoid large, high-carbohydrate meals on an empty stomach.
• Movement. A walk after meals helps your muscles take up glucose and steadies the response.

Medicines and supplements

Medication is rarely needed, and no supplement is established as a treatment. Cutting down on alcohol, which can both cause lows and mask them, and on caffeine, which can make the shaky symptoms worse, helps some people.