Input:   Na   mEq/L Cl   mEq/L HCO3   mEq/L Baseline Gap   mEq/L

Results:   Anion Gap   mEq/L Delta Gap   mEq/L Delta HCO3   mEq/L Delta Delta Ratio   % fraction ratio   Decimal Precision: 0 1 2 3

It is important to know the subject's baseline or premorbid Anion Gap to accurately understand the acid-base disorders suggested by the Delta Delta Ratio.
 
A Delta Delta Ratio between 1-2 usually indicates:

• Uncomplicated high Anion Gap metabolic acidosis.
• Diabetic Ketoacidosis typically has a ratio close to 1.
• Lactic acidosis typically has a ratio around 1.6 due to intracellular hydrogen ion buffering.

 
A Delta Delta Ratio greater than 2 usually indicates:

• HCO3 is higher than expected compared to the rise in the Anion Gap.
• Concurrent metabloic alkalosis, as in vomiting.

 
A Delta Delta Ratio less than 1 may indicate:

• Ketoacidosis resolving with urinary ketone losses.
• Combined high and normal Anion Gap metabolic acidosis.

References

1. Wrenn K. The delta (delta) gap: an approach to mixed acid-base disorders. Ann Emerg Med. 1990 Nov;19(11):1310-3.
2. Breyer JA. Acid base course material. 6th National Critical Care Medicine Review Course.