Blood Sugar Log

Track and monitor your blood glucose readings over time. Log fasting, before-meal, after-meal, and bedtime values in mg/dL or mmol/L. Visualize trends and get category insights.

Create a profile to start logging

About Blood Sugar Log

Blood Sugar Log is a free, private glucose tracker that runs entirely in your browser. It's designed for people with type 1 or type 2 diabetes, prediabetes, gestational diabetes, or anyone monitoring their blood glucose for general health. Log readings in mg/dL or mmol/L, tag them with the right context — fasting, before meal, after meal, bedtime, or random — and watch your trend chart reveal patterns over days and weeks. Multiple profiles let you track your whole family from one device. Everything stays in your browser via IndexedDB; nothing is ever uploaded to a server.

Blood Glucose Targets (Adults without diabetes)

Low (Hypoglycemia)

Below 70 mg/dL (3.9 mmol/L)

Normal Fasting

Below 100 mg/dL (5.6 mmol/L)

Prediabetes (Fasting)

100–125 mg/dL (5.6–6.9 mmol/L)

Diabetes (Fasting)

126 mg/dL or higher (7.0 mmol/L+)

Normal Post-meal (2hr)

Below 140 mg/dL (7.8 mmol/L)

Diabetes Post-meal

200 mg/dL or higher (11.1 mmol/L+)

Based on American Diabetes Association (ADA) guidelines. This tool is for informational purposes only — always consult your healthcare provider for personal targets.

How to Use the Blood Sugar Log

  1. Create a profile for yourself or a family member, and choose your preferred unit (mg/dL or mmol/L).
  2. Click Add Reading after each glucose check.
  3. Enter the value and pick the context — fasting, before meal, after meal, bedtime, or random — so the category is calculated correctly.
  4. Add optional notes (e.g. "after exercise", "before insulin", "had pasta").
  5. Use the context filter and date range to focus on specific patterns.
  6. View the trend chart to spot highs and lows over time. Each dot is colored by category.
  7. Export your data as CSV to share with your doctor or import it into another tool.

Frequently Asked Questions

Is my data private?

Yes. Every reading is stored locally in your browser using IndexedDB. Nothing is sent to any server, and clearing your browser data will delete the log permanently — so export to CSV regularly.

What's the difference between mg/dL and mmol/L?

They are two ways to measure the same thing. mg/dL (milligrams per deciliter) is common in the US. mmol/L (millimoles per liter) is used in most other countries. Conversion: mg/dL ÷ 18 = mmol/L.

Why does context matter?

Normal blood sugar ranges depend on when you measured. A fasting reading of 130 is concerning, but the same reading two hours after a meal is normal. Picking the right context lets the tool flag the right category.

When should I check my blood sugar?

It depends on your treatment plan. Common times are first thing in the morning (fasting), before meals, 2 hours after meals, and at bedtime. Your doctor will recommend a schedule based on your needs.

What is hypoglycemia?

Hypoglycemia means low blood sugar — typically under 70 mg/dL (3.9 mmol/L). Symptoms include shakiness, sweating, confusion, and fast heartbeat. Treat immediately with 15g of fast-acting carbs and recheck in 15 minutes. Seek medical help if symptoms are severe.

Can I track multiple people?

Yes — create a separate profile for each person. Each profile has its own unit preference and reading history. Switch between profiles in the sidebar.

Does this replace a glucose meter or CGM?

No. This tool only logs and visualizes readings — you still need a glucose meter or continuous glucose monitor (CGM) to measure your levels. Use this log to organize and review the data those devices produce.