Diabetes Complications: What to Monitor

Diabetes is not just about glucose. Over time, elevated blood sugar can damage blood vessels, nerves, kidneys, eyes, and the heart. The good news is that regular blood test monitoring helps detect complications earlier, when they can still be slowed or stopped.

Why monitoring complications matters

Even well-controlled diabetes can eventually cause micro- and macrovascular complications. Studies show that a 1 percentage point reduction in HbA1c lowers microvascular complication risk by approximately 37 percent. However, HbA1c alone does not reveal the full picture -- other organ system markers need to be tracked as well.

Kidneys: early warning signs

Diabetic nephropathy is the most common cause of kidney failure in developed countries. Key markers include:

• Creatinine and eGFR: eGFR shows how well the kidneys filter blood. A drop below 60 mL/min indicates moderate kidney dysfunction.
• Urine albumin (microalbuminuria): the earliest sign of diabetic nephropathy -- detectable before eGFR starts declining.
• Cystatin C: more sensitive than creatinine in early stages, especially when muscle mass is low.

Heart and blood vessels

Diabetics face 2 to 4 times higher cardiovascular disease risk. Key markers to track:

• Lipid panel: LDL cholesterol, triglycerides, and non-HDL cholesterol. Diabetics often have an atherogenic profile -- high triglycerides with low HDL.
• ApoB: a more precise atherogenic risk marker than LDL cholesterol, especially when triglycerides are elevated.
• hs-CRP: chronic inflammation is an additional cardiovascular risk factor.

Nerves: peripheral neuropathy

About 50 percent of diabetics eventually develop peripheral neuropathy. Blood tests can help:

• HbA1c: long-term glycemic control indicator -- the better the control, the lower the neuropathy risk.
• Vitamin B12: deficiency is common with metformin use and can mimic or worsen neuropathy.
• Vitamin B1 (thiamine): deficiency is associated with diabetic neuropathy; diabetics have higher B1 deficiency risk.

Eyes and other organs

Diabetic retinopathy is the most common cause of blindness in working-age adults. While blood tests do not directly assess the eyes, good glycemic and blood pressure control (monitored through HbA1c and kidney markers) is the best prevention.

Practical checklist

1. HbA1c -- check every 3 to 6 months. Target is usually below 7 percent (53 mmol/mol). 2. Creatinine + eGFR -- every 6 to 12 months. 3. Urine albumin -- annually, if no known kidney damage exists. 4. Lipid panel -- at least once a year; more often if taking medication. 5. Vitamin B12 -- annually, if using metformin. 6. hs-CRP -- once a year to assess chronic inflammation level.

When to act immediately

If eGFR drops sharply (more than 25 percent over a few months), creatinine rises significantly, or substantial albuminuria develops -- seek urgent nephrology consultation. This may indicate rapid kidney function decline requiring immediate treatment.

Questions for your doctor

1. Does my current HbA1c level adequately protect against complications? 2. How often should kidney function (eGFR, albuminuria) be tested? 3. Does my lipid profile indicate elevated cardiovascular risk? 4. Should I monitor B12 given that I take metformin? 5. What additional tests would help assess diabetic neuropathy risk?