Diabetes is diagnosed when the fasting blood sugar is more than 126mg/dL and post meal glucose level is more 200 mg/dL. FBS measures the glucose levels after 8-10 hours of fasting. It provides a baseline measurement of how much sugar is in your blood without the influence of food. It helps to assess whether you are suffering from prediabetes or diabetes. In some persons we see that FBS or the fasting sugar levels are found to be higher than the post-meal values. This can occur due to various reasons.
1. Can be due to high levels of glucose release from the liver at night which is a sign of insulin resistance.
2. If the person has taken very heavy meals that too late at night can also lead to higher FBS.
3. High levels of hormones including Cortisol, growth hormone at night can lead to higher FBS.
4. In some persons due to the effect of medicines, sugar levels can drop at night leading to a rebound effect causing higher fasting levels in the morning -This is termed as Somogyi effect.
5. In the early morning hours due to the influence of hormones released in our body, sugar levels can go up leading to higher fasting levels. This is termed as Dawn phenomenon.
6. In prediabetes condition termed as Impaired fasting glucose, the fasting blood sugar can go high ranging from 100 to 125 mg/dL. But their post meal sugar levels will remain normal.
7. The effect of certain medications like insulin and sulphonylurea drugs can cause low sugar levels at night leading to a rebound effect causing higher fasting levels.
Hence if you find abnormality in FBS, consult your doctor and find out the reason for it. If you are already on diabetic medications you may need fine adjustments of it to avoid this problem.
Dr. Deepa G, MHSc (Diab), Dip (Diab)