Is Sardines Safe for Kidney Stones? (Safe)
mg oxalate
per serving
Serving: 3 oz (85 g)
Verdict: 🟢 Safe
Per 100g: 5 mg
Data: Harvard T.H. Chan SPH (2024)
What this means: Sardines is rated Safe (🟢). At 4 mg oxalate per serving, it's well under the 25 mg safety threshold. You can include it regularly in a kidney stone diet. Pair it with calcium-rich foods (dairy, fortified plant milks) for additional protection, and drink plenty of water throughout the day.
Among seafood, Sardines sits well above the category average of 2 mg. For context, 55 out of 55 seafood (100%) are rated 🟢 Safe (under 25 mg oxalate/serving). The average seafood in our database has 2 mg oxalate per serving — which means Sardines is 158% above the category norm. Within its specific category, Sardines ranks on the higher end for oxalate. This context matters because two 'Safe' foods can have very different oxalate levels — one might have 5 mg while another has 24 mg. Both are Safe, but the first gives you more dietary flexibility. Browse all seafood rated Safe to compare within the same verdict level.
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. Sardines comes in at 4 mg oxalate per 3 oz (Safe) in the measured database.
Can I eat this food every day?
If it's in the Safe zone (under 25 mg/serving), yes — it can be a regular part of your diet. For Caution or Avoid foods, frequency matters. Rotate them with lower-oxalate options throughout the week. Sardines comes in at 4 mg oxalate per 3 oz (Safe) in the measured database.
Where does the oxalate data come from?
Harvard T.H. Chan School of Public Health (2024) via the OHF database. These are direct laboratory measurements — the most reliable oxalate data available for food. For context, Sardines measures 4 mg per 3 oz, rated Safe.
Should I also check sodium and calcium?
Definitely. Oxalate is only part of the story — high sodium raises calcium in urine, and dietary calcium (from food, not pills) binds oxalate in the gut. The food's main page lists both, so it's worth checking before you plan around it. Sardines comes in at 4 mg oxalate per 3 oz (Safe) in the measured database.