Metformin

Metformin is a widely used oral medication for the treatment of DM2 (Type 2 diabetes mellitus) and, in some cases, PCOS (polycystic ovary syndrome). While insulin helps lower blood sugar levels by helping cells absorb sugar from the blood, metformin lowers blood sugar by reducing sugar production in the liver and improving the body’s response to insulin.

Unlike many other diabetes medications, metformin does not stimulate insulin secretion, significantly reducing the risk of hypoglycemia (low blood sugar). In plain words, metformin alone doesn’t cause low blood sugars.

Metformin and Diving

Although metformin is generally well tolerated, divers using it must consider its effects under hyperbaric and immersion conditions. The key concerns for scuba divers include lactic acidosis, thermoregulation, dehydration, and hypoglycemia when combined with other medications for diabetes.

Risk of Lactic Acidosis

One rare but serious side effect of metformin is lactic acidosis — a condition in which lactic acid builds up in the bloodstream, leading to metabolic acidosis. While the overall incidence is low, diving presents several physiological stressors that could increase this risk, including:

• Hypoxia (low oxygen levels)
• Hypercapnia (high carbon dioxide levels)
• Increased anaerobic metabolism from exertion (e.g., swimming against currents)
• Impaired kidney function (which can reduce metformin clearance)

If anaerobic metabolism and carbon dioxide retention occurs, it may theoretically exacerbate lactate accumulation, especially in divers with impaired renal function.

Impaired Thermoregulation and Dehydration

Metformin reduces hepatic glucose output, impairing the body’s ability to produce heat under cold conditions. This effect, combined with the increased heat loss associated with immersion, may increase a diver’s susceptibility to hypothermia.

Additionally, metformin-associated gastrointestinal side effects (such as diarrhea or nausea) can contribute to dehydration, which is already a common concern in diving due to dry breathing gases and immersion diuresis (increased urine production underwater). Dehydration can impair circulation, slow nitrogen elimination, and increase decompression sickness risk.

Risk of Hypoglycemia

While metformin alone does not typically cause hypoglycemia, when combined with other glucose-lowering medications such as insulin or sulfonylureas, there is a risk of dangerously low blood sugar levels underwater. Symptoms of hypoglycemia—dizziness, confusion, weakness, and loss of consciousness—can be life-threatening in a diving environment.

Factors that could increase the risk of hypoglycemia while diving include:

• Skipping meals before a dive
• Extended dive times leading to prolonged fasting
• Increased exertion consuming glucose faster than usual
• Co-administration with insulin or sulfonylureas

Implications in Diving