**Core Concept**
Heparin is a highly effective anticoagulant medication that works by inhibiting thrombin and factor Xa in the coagulation cascade. Its adverse effects are primarily related to its anticoagulant properties, leading to bleeding complications.

**Why the Correct Answer is Right**
The correct answer is **B. Hyperkalemia**. Heparin does not directly cause hyperkalemia, which is a known adverse effect of other medications such as ACE inhibitors and potassium-sparing diuretics. Heparin's anticoagulant effects are mediated through its binding to antithrombin III, which inhibits the coagulation cascade. In contrast, heparin can cause bleeding complications, including oozing from injection sites, gastrointestinal bleeding, and intracranial hemorrhage.

**Why Each Wrong Option is Incorrect**
* **Option A:** Osteoporosis is a known adverse effect of long-term heparin therapy, particularly in pregnant women.
* **Option C:** Thrombocytopenia is a rare but serious adverse effect of heparin, known as heparin-induced thrombocytopenia (HIT).

**Clinical Pearl / High-Yield Fact**
To remember the common adverse effects of heparin, use the "OOPS" mnemonic: Osteoporosis, Oozing from injection sites, Platelet dysfunction (thrombocytopenia), and Serious bleeding complications.

**Correct Answer: B. Hyperkalemia**