High & Low Sugar Level With High Blood Pressure

by Kerry

Original Question

I was recently diagnosed with diabetes after a blood sugar of 310 mg/dL and glucose in my urine. I was started on metformin and another diabetes medicine, but metformin makes me feel sick. My fasting readings are about 135–175, after breakfast 248–284, and at night sometimes 94–124. I feel shaky, hungry and unwell around 94, but when my glucose is very high I sometimes feel fine. I also have high blood pressure and a rapid heartbeat. What is happening?

Quick Answer:

Your readings show significant hyperglycemia, while 94 mg/dL is not true hypoglycemia. Because your body may have become accustomed to much higher glucose levels, a rapid fall toward normal can sometimes cause hunger, shakiness or a “low” feeling even when the meter is above 70 mg/dL. Your medicines and symptoms should be reviewed promptly by your doctor rather than changing doses on your own.

Answered by:
Dr. Albana Greca, MD, MMedSc

Family Physician, IDF Fellow

Why Do I Feel Low at 94 mg/dL?

A glucose of 94 mg/dL is not hypoglycemia. Low blood sugar is generally defined as below 70 mg/dL. However, when glucose has been running very high for some time, the body can react to a rapid fall toward normal with symptoms such as hunger, shakiness, tingling, sweating or a racing heart.

This does not mean you should deliberately keep your glucose high. The goal is gradual, safe improvement under medical supervision. Our guide to
blood glucose targets
can help you understand the difference between a normal value and a true low.

Why Do I Feel Fine When Glucose Is 300–400?

High glucose does not always cause obvious symptoms. Some people can feel relatively well even when readings are dangerously elevated. That does not make the level safe. Persistent hyperglycemia can cause dehydration and, over time, damage the eyes, kidneys, nerves, heart and blood vessels.

Readings around 300–400 mg/dL deserve prompt medical review. If glucose reaches these levels repeatedly, especially with illness or dehydration, your treatment plan needs reassessment.

Could Metformin Be Making You Sick?

Metformin commonly causes gastrointestinal side effects such as nausea, abdominal discomfort and diarrhea, particularly when treatment is first started or the dose is increased. These problems can sometimes improve with gradual dose adjustment or an extended-release formulation, but any change should be made by your prescriber.

Do not return to a previous dose or stop treatment on your own. Bring your glucose log and the exact names and doses of all your medicines to one clinician so the whole plan can be reviewed.

What Should You Do Now?

Contact your doctor promptly to review your medications and side effects.

Record fasting, before-meal and 2-hour post-meal readings.

Ask about your HbA1c and kidney function if not already checked.

Do not double, skip or restart doses without medical advice.

Keep hydrated unless a doctor has restricted your fluids.

Using the correct technique described in our
home blood glucose monitoring guide
can make your glucose log more reliable for medication decisions.

Be Careful With Exercise When Glucose Is Very High

Regular activity is important for diabetes, but vigorous exercise is not the right response to every high reading. If glucose is above about 240 mg/dL, especially in people at risk of ketosis, checking for ketones may be necessary. If ketones are present, strenuous exercise can make hyperglycemia worse.

For that reason, do not try to “run the sugar down” when readings are very high. Follow your clinician's exercise plan and review persistent highs medically.

When Is Urgent Medical Care Needed?

Seek urgent medical care if very high glucose is accompanied by vomiting, worsening weakness, confusion, difficulty breathing, severe dehydration, abdominal pain, inability to keep fluids down or unusual drowsiness. A persistent rapid heartbeat together with feeling faint, chest pain or shortness of breath also needs urgent assessment.

My Practical Advice

The most important step is not to choose between the first and second medication plans by yourself. Take your recent readings, symptoms and exact medication doses back to one doctor who can review the whole picture. A glucose of 94 mg/dL is not too low, but your symptoms during rapid glucose changes are worth discussing.

Because your readings vary widely, it may also help to compare them with
blood sugar patterns through the day
rather than focusing on one isolated number.