by Kat
(USA)
QUESTION: Today I woke up with a headache. After taking Tylenol and eating sausage gravy and biscuits with orange juice, I felt worse. I became shaky, dizzy, and nauseated. About an hour after eating, my dad checked my blood sugar and it was 99 mg/dL. My dad has diabetes, and diabetes also runs in my mother's family. Is 99 bad an hour after eating? This seems to happen more often, and I feel tired and weak all the time.
A blood sugar of 99 mg/dL (5.5 mmol/L) one hour after eating is not high and not hypoglycemia. By itself, it does not show that diabetes caused your symptoms.
One home reading after a meal cannot diagnose or rule out diabetes. Because diabetes runs in your family and these episodes are recurring, I would arrange a medical check-up and ask about a fasting laboratory glucose and HbA1c.
If symptoms happen again, check your glucose as soon as possible. A level below 70 mg/dL (3.9 mmol/L) is considered low.
Answer by Dr. Albana Greca, MD, MMedSc
Hi Kat,
Your reading of 99 mg/dL does not show either very high or very low blood sugar. The more important issue is that the shaking, dizziness, nausea, weakness, and tiredness are happening repeatedly.
| Reading | Timing | Meaning |
|---|---|---|
| 99 mg/dL | About 1 hour after breakfast | Not low or high, but not a diagnostic diabetes test |
A one-hour reading after an ordinary meal is not one of the standard tests used to diagnose diabetes. Food, activity, stress, illness, and timing can all affect the result.
This is why I would not use 99 mg/dL to diagnose or rule out diabetes. Our guide to whether a blood sugar reading is normal explains why timing matters.
Shaking, dizziness, sweating, hunger, weakness, and headache can occur with hypoglycemia, but 99 mg/dL is not low blood sugar. A glucose below 70 mg/dL is considered hypoglycemia.
It is possible that your glucose changed before it was tested, but we cannot assume that. The most useful reading is one taken while the symptoms are happening.
No. Family history increases your risk, but it does not mean you have diabetes. Diagnosis is made with accepted laboratory tests such as fasting plasma glucose or HbA1c.
| Test | Normal | Prediabetes | Diabetes range* |
|---|---|---|---|
| Fasting glucose | Below 100 | 100–125 | 126 mg/dL or higher |
| HbA1c | Below 5.7% | 5.7–6.4% | 6.5% or higher |
*Diabetes usually requires confirmation when there is no clear hyperglycemic crisis.
A fasting blood sugar test and HbA1c would be more useful than repeating random after-meal checks.
These symptoms are not specific to diabetes. They can occur with dehydration, infection, anemia, low blood pressure, thyroid problems, migraine, anxiety, medication effects, poor sleep, and other conditions.
Because the episodes are becoming more frequent and you feel tired and weak much of the time, I would not assume blood sugar is the only possible cause.
Seek urgent medical care if the symptoms occur with fainting, confusion, trouble speaking, one-sided weakness, chest pain, difficulty breathing, a sudden severe headache, repeated vomiting, or seizure.
Kat, a glucose of 99 mg/dL one hour after breakfast is not concerning by itself and does not show that diabetes or hypoglycemia caused your symptoms.
Because these episodes are recurring and you feel persistently tired and weak, I would check a fasting laboratory glucose and HbA1c and also look for other possible causes.
Medical review: Dr. Ruden Cakoni, MD, Endocrinologist
Last reviewed: August 2026.
Educational safety note: This answer is for general diabetes education only and does not replace personal medical advice, diagnosis, or treatment. Recurrent or worsening symptoms should be assessed by a healthcare professional.
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