by Alice
(Los Angeles, ca, u.s.a.)
Answer by Dr. Albana Greca, MD
Hello Alice,
Your afternoon glucose of around 145 mg/dL is much less concerning to me than the repeated morning readings in the 40s and 50s.
A blood glucose below 70 mg/dL is considered hypoglycemia. A reading below 54 mg/dL represents clinically significant hypoglycemia.
Therefore, readings such as 45 or 57 mg/dL should not be ignored, particularly if you also experience sweating, shaking, weakness, hunger, dizziness, blurred vision, palpitations, headache, confusion, or unusual tiredness.
If you are not taking insulin or diabetes medicines that lower glucose, repeated low readings need further investigation.
No. A glucose of 145 mg/dL after eating does not diagnose diabetes. Blood sugar naturally rises after carbohydrates are eaten, and the meaning of the result depends on how long after the snack you tested.
| Reading | Interpretation |
|---|---|
| 45–57 mg/dL | Too low and should be evaluated if repeated |
| Below 70 mg/dL | Hypoglycemia |
| 145 mg/dL after food | Can occur after eating and is not diagnostic by itself |
It can contribute. Going for long periods without food and then eating a larger amount may produce wider swings in glucose. However, I would not assume that your eating pattern is the only explanation for readings as low as 45 mg/dL.
Other possibilities include an inaccurate meter reading, alcohol intake, certain medicines, prolonged fasting, intense exercise, and less commonly disorders involving the liver, adrenal glands, hormones, or excess insulin production.
I would start with regular, balanced eating rather than long periods of fasting followed by overeating. Try to:
Home glucose meters are useful but are not perfectly accurate. Wash and dry your hands before testing, use strips that are not expired, and repeat an unexpectedly low result.
Because you are repeatedly obtaining values below 70 mg/dL, I would also ask your doctor for a laboratory glucose evaluation rather than relying only on your home meter.
Your readings alone do not establish diabetes. Diabetes is normally diagnosed using laboratory testing such as fasting plasma glucose, HbA1c, or an oral glucose tolerance test.
A fasting glucose of 126 mg/dL or higher on appropriate testing, or an HbA1c of 6.5% or higher, can indicate diabetes when the result is confirmed as appropriate. Your pattern of very low morning glucose followed by a moderate rise after eating is not the typical way diabetes is diagnosed.
Because you have recorded glucose values in the 40s and 50s, I recommend discussing them with your doctor and bringing a written glucose and food diary. Testing may include fasting glucose, HbA1c, and other investigations depending on your symptoms and medical history.
Other readers also ask about low fasting blood sugar, glucose changes after meals, and whether isolated high readings mean diabetes.
Learning the difference between fasting, post-meal, and random blood glucose readings can help you interpret home glucose measurements more accurately and know when laboratory testing is needed.
Last medically reviewed: August 2026
Click here to post comments or follow up
Ask the Doctor now? Simply click here to return to Diabetes Test and Levels.