Fasting for an OGTT test: what to know

OGTT means oral glucose tolerance test. During pregnancy, it checks how your body handles a measured glucose drink. The preparation matters because food, drinks, activity and some medicines can affect the blood glucose readings.

Fasting means not eating during the time stated by your testing centre before the appointment. Do not assume that coffee, tea, juice, chewing gum or sweets are acceptable; ask the centre what you may drink. Water may be allowed, but follow the instruction you were given.

At the appointment, staff may take an initial blood sample, give you the glucose drink, and collect further samples after set waiting periods. Remain seated and avoid eating, strenuous activity and extra drinks unless staff say otherwise. Bring something to eat for after the final sample.

Confirm the appointment instructions in advance, including when to stop eating, which drinks are allowed, and whether your usual medicines should be taken. Tell the clinic if you have diabetes, feel unwell, or need advice about a medicine before changing your routine.

Eat your usual meals before the fasting period unless your clinician has advised a different plan. Avoid arranging exercise during the test, and allow enough time to stay at the centre until all samples are collected. If you accidentally eat or drink something outside the instructions, report it rather than hiding it; the team can decide whether the test should continue or be rearranged.

Tell the testing staff promptly if you become dizzy, shaky, sweaty, weak, nauseated or faint during fasting or while waiting. Sit or lie down as directed, and do not leave the centre alone while you feel unwell.

Contact your maternity team for advice if vomiting, illness or a medicine issue prevents you from fasting or keeping the glucose drink down. Seek urgent help for loss of consciousness, severe breathing difficulty, chest pain or a serious allergic reaction.

Ask: When should I stop eating? Which drinks are allowed? Should I take my regular medicines before the appointment? What should I do if I vomit, feel faint, or accidentally break the fast? When and how will I receive the result?