Is Blueberries (Fresh or frozen) Safe for Kidney Stones?
mg oxalate
per serving
Serving: 1 cup (200 g)
Verdict: 🟡 Caution
Per 100g: 14 mg
Data: Harvard T.H. Chan SPH (2024)
In practical terms, Blueberries (Fresh or frozen) sits in the 25-99 mg range with 27 mg per serving, so treat it as a sometimes-food. Keep servings modest, don't stack it with other moderate-oxalate items in one day, and pair it with calcium to blunt absorption.
Why does the safe threshold matter?
The 25 mg per serving threshold is based on clinical guidance for kidney stone patients. Harvard's lab data (2024) provides the most reliable oxalate measurements available — no database estimates, direct lab analysis. For context, Blueberries (Fresh or frozen) measures 27 mg per 1 cup, rated Caution.
Can I eat this food every day?
For Safe foods (under 25 mg/serving), daily use is generally fine. Caution and Avoid foods work better as occasional items — rotate them with safer options so no single high-oxalate food becomes a habit. Applied to Blueberries (Fresh or frozen): 27 mg oxalate per 1 cup — Caution per Harvard (2024).
Where does the oxalate data come from?
The numbers come from Harvard T.H. Chan SPH's 2024 laboratory measurements, published through the OHF database. Direct lab analysis, which is why they're treated as the reference values for food oxalate. Blueberries (Fresh or frozen) comes in at 27 mg oxalate per 1 cup (Caution) in the measured database.
Should I also check sodium and calcium?
Yes — oxalate alone doesn't decide stone risk. Sodium pushes more calcium into urine, and calcium from food (not supplements) helps bind oxalate during digestion. The main food page covers sodium and calcium alongside oxalate. Blueberries (Fresh or frozen) comes in at 27 mg oxalate per 1 cup (Caution) in the measured database.