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Functional Medicine Doctor in New York, NY
Medically reviewed by Dr. David Borenstein, MD. Last reviewed October 2026.
What is Functional Medicine?
Functional medicine is evidence-based healthcare that targets the root cause behind your symptoms, rather than merely suppressing them indefinitely.
Functional Medicine at Manhattan Integrative Medicine
So many patients come into Manhattan Integrative Medicine because they’ve heard an amazing recovery story from a friend. But they still ask: What is functional medicine?
Dr. Borenstein likes to cite the Institute for Functional Medicine's clear and simple MO: “One condition, many causes. One cause, many conditions.”
That's why Dr. Borenstein will always take the time to determine how and why your illness developed, before restoring your health by addressing its root cause.
This requires being a bit of a medical detective – searching for connections between symptoms that may at first glance seem unrelated, but that turn out to share the same root dysfunction. It requires crafting whole body treatments for your unique biological ecosystem – not for some average patient on a statistics chart. Dr. Borenstein was a functional medicine doctor 20 years ago – long before it was trendy – so it's become second nature for him.
He understands that your body's organs and systems function synergistically, not simply as rogue operators in a biological wilderness. He targets your dysfunction as part of a holistic ecosystem, and treats you as a whole person, not just the sum of your symptoms.
Check it out by calling Manhattan Integrative Medicine today at (212) 262-2412 or contact us here.
Background and Explanation of Functional Medicine
What do Functional Medicine doctors do?
When conventional doctors assess a nutrient or hormone level they see it falls inside the “normal range,” then tell you you're fine – despite the fact that you're clearly suffering symptoms. This can leave you struggling with the same chronic conditions for years, specialist appointment after specialist appointment – each one looking only at the organ or system he or she was trained to treat.
Dr. Borenstein applies his distinct functional medicine approach to identify and target:
Adrenal Fatigue
Chronic stress, insufficient sleep and poor diet can overstimulate your adrenal glands, disrupt your cortisol and DHEA levels, and cause debilitating pain and fatigue.
Hypothyroidism
An underactive thyroid that is unable to produce the amount of thyroid hormones your body requires, causing weight gain, fatigue, muscle weakness, high cholesterol, joint pain or stiffness, and depression.
Fibromyalgia
Chronic muscle shortening caused by either nerve chemical signals in the spinal fluid or by explosive synchronization (ES) that stimulate a hyperactive brain to experience extreme pain, stiffness and recurring infections.
Arthritis
Inflammation of one or more joints causing pain, stiffness and immobility.
Small Intestine Bacterial Overgrowth (SIBO)
SIBO (small intestinal bacterial overgrowth) is an excess of bacteria in the small intestine. The bacteria ferment food too early, causing bloating, gas, abdominal pain, and diarrhea or constipation.
Crohn's Disease
Inflammation of the digestive tract which can lead to abdominal pain, severe diarrhea, fatigue, weight loss and malnutrition.
Hormonal Imbalances
Andropausal men and men with low T require testosterone supplementation with BHRT; menopausal women may require estrogen, testosterone, and progesterone supplementation with BHRT.
Polycystic Ovary Syndrome
A hormonal disorder that can cause infrequent or prolonged menstrual periods or excess androgen levels, and irregular release of eggs by ovary follicles.
Hashimoto's Thyroiditis
An autoimmune condition in which the immune system attacks the thyroid, the most common cause of hypothyroidism in the U.S., leading to fatigue, weight gain, cold intolerance and hair loss.
Chronic Fatigue Syndrome
Profound exhaustion lasting six months or longer that rest doesn't relieve and exertion makes worse, often with unrefreshing sleep and trouble concentrating.
Mold Exposure
Breathing in mold spores and the toxins some molds produce, usually in water-damaged buildings, which can cause fatigue, brain fog, sinus problems, headaches and joint pain.
Long COVID
Symptoms that persist or appear weeks to months after a COVID-19 infection, such as fatigue, shortness of breath, brain fog and heart palpitations.
Type 2 Diabetes
Insulin resistance that keeps blood sugar elevated and, over time, raises the risk of heart, kidney, nerve and eye damage.
Dr. Borenstein also knows how to treat hormone imbalance during the natural life stages of menopause and andropause, and excels at chronic pain treatment as well as mitigating the effects of insomnia.
Your Functional Medicine Treatment Plan
First, Dr. Borenstein will listen. He'll examine you, review your medical history and order any required bloodwork.
Once he has detected your root cause, he may explain in detail, then deliver one or more of the following:
- Bioidentical Hormone Replacement Therapy for Women
- Bioidentical Hormone Replacement Therapy for Men
- Low Dose Naltrexone Therapy
- Relaxation Technique Protocols
As with any medical treatment, your results will vary based on your age, genetics, general health, environmental conditions, and follow up care.
Reserve Your Appointment
Treat your whole body to the functional medicine solution. Schedule an appointment with Dr. Borenstein today at (212) 262-2412 or contact us here.
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