The content provided on this blog is intended for educational purposes only and should not be construed as medical advice. We strongly advise readers to seek guidance from a qualified healthcare professional regarding any medical concerns.

To reflect its medicinal nature rather than recreational use, we prefer the term ‘medical cannabis’ over terms such as ‘marijuana’, “grass”. or ‘dope’ which may carry negative connotations.

The opinions expressed in the blog belong to the respective authors, who are not medical professionals, and may not necessarily align with those of Lyphe Clinic. Lyphe Clinic does not endorse any specific products or services mentioned, except those provided through Lyphe Clinic.

Readers should be aware that the legality of medical cannabis varies by location, and this disclaimer may be subject to periodic updates.

Key Points

  • Medical cannabis offers a myriad of therapeutic benefits, but it may not be the best choice in certain scenarios.
  • For adolescents, as well as pregnant and nursing individuals, it’s advisable to abstain from marijuana.
  • For individuals with certain mental disorders, such as schizophrenia or bipolar disorder, it may be beneficial to consult with a physician before using any form of cannabis.
  • Medical cannabis may interact with other medications and cause adverse side effects.
  • Those with a history of lung, kidney, heart, or liver disease should be aware that cannabis may exacerbate these conditions and should consult with a physician before beginning treatment.

In the UK, the conversation around cannabis is evolving, reflecting shifts in public opinion, medical research, and legal considerations. As more people become curious about its potential benefits and risks, the need for comprehensive education and understanding about its use has never been more vital. While it has shown promising potential in treating health conditions, there are certain situations where using weed may be detrimental.

In this blog post, we explore when it is best to avoid the use of marijuana. We also discuss the significance of responsible use, as well as how to use medical cannabis safely.

Medical Weed and Illegal Weed: What You Should Know

When it comes to discussing marijuana, it is crucial to understand the distinction between medical weed, which is used for therapeutic purposes under medical supervision, and illegal weed, which is obtained and used without proper authorisation. 

Legal Status

  • Medical marijuana is legal in certain jurisdictions and is regulated under specific laws and regulations. It requires a recommendation or prescription from a healthcare professional, and patients must obtain medical cannabis from authorised dispensaries or pharmacies.
  • Illegal marijuana refers to cannabis obtained, possessed, or used without complying with the local laws and regulations. It is not authorised for medical use and may lead to legal consequences.

Quality Control

  • Medical weed undergoes strict quality control measures to ensure safety, purity, and consistency. It is cultivated, processed, and distributed by licenced producers who follow standardised procedures and testing protocols.
  • Illegal weed lacks quality control measures, making it difficult to determine its potency, purity, and safety. It may be contaminated with harmful substances or pesticides, posing potential health risks.

Cannabinoid Profile

  • Medical cannabis is cultivated to have specific cannabinoid profiles, with varying levels of THC (tetrahydrocannabinol) and CBD (cannabidiol), among other cannabinoids. These profiles can be tailored to meet individual patient needs for therapeutic purposes.
  • Illegal cannabis may have inconsistent and unpredictable cannabinoid profiles, as it is often sourced from unregulated and unverified suppliers. The levels of THC and CBD can vary greatly, potentially leading to unexpected effects.

Medical Supervision

  • Medical marijuana is used under the supervision of healthcare professionals who have expertise in cannabis therapeutics. They guide dosage, administration methods, and monitoring for potential side effects or interactions.
  • The use of illegal marijuana lacks medical supervision, and individuals may self-administer without proper knowledge or understanding of its potential risks, interactions, or appropriate dosages.

Therapeutic Intent

  • Medical weed is utilised for specific therapeutic purposes, such as managing chronic pain, alleviating symptoms of certain medical conditions, or improving quality of life. It is prescribed or recommended based on individual patient needs and medical conditions.
  • Illegal weed is often used recreationally for non-medical purposes, seeking the psychoactive effects of THC or other recreational purposes. Its use does not involve medical guidance or specific health goals.

Medical Weed and Illegal Weed: A Summary Table

Feature Medical Cannabis Illegal Cannabis
Source Licensed and regulated producers and dispensaries Unregulated, often from black market sources
Quality Control Subject to rigorous testing for purity and potency No guaranteed quality or safety standards
Purpose Prescribed for specific medical conditions Recreational or self-medication without prescription
Legal Status Legal in many regions with a valid prescription Illegal in many regions regardless of use
THC/CBD Levels Controlled and labelled for specific therapeutic needs Varies widely, no standardisation
Safety Reduced risk of contaminants like pesticides and mold Potential for contamination and adulteration
Access Dispensaries, pharmacies, or specific retailers Street dealers, online illicit market
Usage Monitoring Often monitored by healthcare professionals No monitoring or professional guidance
Taxation and Pricing Often taxed; prices can be standardised Prices can vary widely; no taxation
Packaging Labelled with content, dosage, and warnings Often unlabelled or misleadingly labelled

Lyphe’s Approach to Responsible Cannabis Use

Lyphe Clinic Logo.

At Lyphe, we are committed to promoting responsible use and ensuring the well-being of our patients. Our approach encompasses the following:

  • Patient education and support: Our team of medical professionals and educators are available to address any concerns patients may have. For instance, we provide complete information on dosage, administration methods, and potential interactions with other medications.
  • Monitoring and managing treatment plans: Regular follow-up appointments allow us to monitor the patient’s progress, evaluate any potential side effects, and make necessary modifications to the treatment plan. This proactive approach ensures that patients receive the most effective and appropriate care, maximising the therapeutic benefits of medical cannabis while minimising potential risks.
  • Legal and safe access: We work closely with authorised healthcare professionals, ensuring that patients receive the necessary approvals and prescriptions.

If you would like to know more about our approach to responsible and effective cannabis use, schedule an appointment with one of our experts today!

Understanding Medical Cannabis

Infographic comparing THC and CBD.

Medical cannabis refers to the use of the cannabis plant and its components, such as THC (tetrahydrocannabinol) and CBD (cannabidiol), for the treatment of certain health conditions. More specifically, the Cannabis sativa plant has seen medical use for thousands of years, and clinical data has provided insights into its potential therapeutic benefits. It’s important to note that medical weed is different from recreational or non-medical cannabis use.

Healthcare professionals prescribe medical weed to patients who meet specific criteria, aiming to relieve their symptoms and elevate their overall quality of life. It is used in controlled and regulated environments, ensuring appropriate dosage, strain selection, and administration methods for each individual’s unique needs. This approach aims to harness the medicinal potential of cannabis while minimising any potential risks or side effects.

The following are some of the uses and benefits of medical marijuana in a controlled and medical environment:

Condition Benefits
Chronic pain management Cannabis can provide relief for patients with chronic pain conditions.
Nausea and vomiting Cannabinoids can activate receptors in the brain and gastrointestinal system, alleviating nausea and vomiting in patients undergoing chemotherapy.
Epilepsy Medical marijuana has muscle relaxant properties, which is helpful for patients with multiple sclerosis (MS) who often experience muscle spasms, stiffness, and difficulty in mobility.

When Not to Use Marijuana: Risks Factors to Watch Out For

Despite the many potential healing benefits of medical cannabis, it is important to understand that there are certain situations and risk factors where its use may not be appropriate. In more serious cases, it may also lead to harm.

In this section, we explore some of these risk factors and discuss why it’s crucial to still exercise caution with cannabis.

Immature Brain Development in Adolescents

Adolescence is a critical period of brain development, and marijuana use during this time can have long-lasting effects. Studies have shown that regular consumption among young individuals can negatively impact brain maturation, cognitive function, and memory.

A 2017 study from the Journal of the American Academy of Child & Adolescent Psychiatry discovered that frequent weed use during the adolescent period, particularly recreational use, can lead to poor cognitive outcomes in adulthood. These effects are shown to be persistent and long-lasting, even when individuals stop using weed.

The endocannabinoid system, which is influenced by marijuana use, plays a crucial role in brain development and is still developing until the mid-20s. Therefore, youngsters should avoid using marijuana before reaching adulthood unless prescribed by a health professional in controlled dosages.

Risk of Mental Health Issues

While some individuals may find relief from certain mental health conditions through marijuana use, it is important to be aware of the potential drawbacks. Research has shown that weed consumption may increase the risk of developing mental health conditions, particularly in susceptible individuals.

To this end, those with a history of the following mental illnesses should be extra cautious when using marijuana:

  • Psychosis
  • Schizophrenia
  • Bipolar disorder
  • Depression

Studies have shown that smoking marijuana increases the risk of developing schizophrenia and other psychotic disorders if used without proper guidance. One 2019 multicentre case-control study published in Lancet Psychiatry suggests that daily cannabis usage was associated with increased odds of psychotic disorder five times more than those who have never consumed weed. Additionally, cannabis may worsen symptoms in individuals already diagnosed with psychological disorders. 

Pregnancy and Breastfeeding

Close-up view of a nurse using a stethoscope on a pregnant mother's abdomen.

Weed use during pregnancy and breastfeeding carries potential implications for both the mother and the developing baby. Studies have shown that exposure to cannabis in the womb can have adverse effects on fetal brain development, leading to long-term cognitive and behavioural consequences. The reason for this is that THC, the psychoactive compound in marijuana, can cross the placenta and pass into the baby’s bloodstream. It is also possible for babies to be exposed to weed in breast milk.

In terms of effects, the long-term consequences on fetal brain development are well-documented in medical literature. For instance, a 2020 review published in Frontiers Psychiatry suggests that pre-natal and post-natal exposure to cannabis can lead to consequences that may carry throughout adolescence. 

These include the following:

  • Low birth weight
  • Increased risk of developing a substance use disorder
  • Cognitive deficits (attention, learning, and memory)
  • Lack of control over emotions and aggression.
  • Affective disorders (depression, anxiety) and psychotic illnesses (schizophrenia)
  • High impulsivity
  • Reduction in head circumference

Moreover, heavy users, particularly those who mix it with tobacco, are at higher risk of giving birth to a premature baby. As such, pregnant and breastfeeding individuals must abstain from consuming weed to safeguard the health and growth of the child.

Respiratory Risks of Smoking Marijuana

Marijuana smoke can adversely affect lung health and has been associated with symptoms such as cough, phlegm production, and wheezing. It contains many of the same toxins and carcinogens found in tobacco smoke. While both substances introduce harmful chemicals, marijuana smoke often leads to a deeper inhalation, potentially causing further lung irritation. 

Moreover, vaping weed, though perceived as a safer alternative, is not without risks. It can introduce harmful chemicals into the lungs, especially if the vaping products are adulterated or improperly manufactured. Additionally, “dabbing”, which involves inhaling marijuana concentrates, can expose users to elevated levels of THC and potential toxins, increasing the risks for respiratory complications.

Interactions With Other Medications

A common question people ask is, “Does weed interact with any medications?” The short answer is yes. Marijuana can interact with certain medications and substances, causing potentially harmful effects. 

More specifically, a 2022 review from the Journal of Clinical Medicine ranked medications from five (no risk) to one (highest risk) for interaction with cannabis:

Risk Medication Uses
5 Rufinamide Anticonvulsant
Topiramate Manage and treat epilepsy and migraine
Zonisamide Antiepileptic 
Nelfinavir Protease inhibitor for HIV
3 Chlorpromazine Used to manage schizophrenia, bipolar disorder, and acute psychosis
Clobazam Seizure control
Clozapine Manage schizophrenia
Eslicarbazepine Anticonvulsant
Hexobarbital Anaesthetic
Indinavir Protease inhibitor for HIV
Ketoconazole Treatment of fungal infections
Methadone Chronic pain management
Rifampicin Antibiotic
Stiripentol Seizure medicine
Theophylline Asthma control
Valproate Used to treat epilepsy and bipolar disorder
2 Buprenorphine Pain management
Tacrolimus Immunosuppressive agent
1 Warfarin Blood thinner


It is important to consult with a healthcare professional or pharmacist to understand any potential interactions between marijuana and any medications you may be taking.

History of Heart, Kidney, or Liver Disease

An elderly man experiencing chest discomfort.

When considering the use of medical cannabis, it is important to take into account any pre-existing health ailments, especially those related to the heart, kidneys, lungs, or liver.

While more research is needed to fully understand the effects of marijuana on these specific conditions, there are several factors to consider:

  • Heart: The use of weed can cause an increase in heart rate and blood pressure, which could potentially pose risks for individuals with existing cardiac diseases.
  • Kidney: Chronic cannabis consumption has been associated with structural and functional changes in the kidneys, but more research is needed to understand the long-term implications.
  • Liver: There is evidence to suggest that marijuana use may have potential effects on liver function, especially in individuals with underlying liver conditions or those at risk of related diseases.

At Lyphe, we provide you with the guidance and advice needed to ensure that you are using medical cannabis in a safe and effective way. Our team can help you select the right strains for your needs, as well as offer tips on how to use them responsibly. 

Schedule an appointment with one of our medical cannabis experts today to see whether this alternative path is right and safe for you.


Medical cannabis holds potential as a treatment option for various health issues when used in a controlled medical environment. However, it is vital to consider the risks and exercise caution, particularly in certain circumstances.

The clinical use of weed is continually being studied and understood, and healthcare professionals play a vital role in guiding patients through their medical cannabis journey. Professionals, like the team at Lyphe, have the expertise to select the right strain, dose, and delivery method to maximise the healing advantages of medical cannabis, all the while reducing potential downsides or side effects.

Book an appointment today to speak with a healthcare expert at Lyphe to learn more about medical cannabis, how it can help you, and the best ways to use it.

Frequently Asked Questions

Can you use weed on antibiotics?

There is limited scientific research on the interaction between cannabis and antibiotics. Some sources suggest that taking THC and antibiotics is generally safe, but others say that it could reduce the effectiveness of the medication. Always seek advice from a medical expert before mixing cannabis with any medications.

Can you use weed on birth control?

While there is limited scientific research directly investigating the interaction between cannabis and birth control, one study published in the journal Life Sciences suggests that estrogen-based birth control may increase sensitivity to THC. This could amplify the “high” but also heighten side effects. Always consult a healthcare professional before combining cannabis with medications, including birth control.

Is it bad to take weed at night?

Some studies suggest that cannabis may improve sleep in certain conditions, such as post-traumatic stress disorder (PTSD), multiple sclerosis, and chronic pain. However, other research indicates that regular marijuana use may disrupt sleep patterns.

Can you use weed with a cold?

It has been suggested that using cannabis may help alleviate general aches and pains, which are common cold symptoms. However, smoking non-medical cannabis can irritate the throat and airways, potentially worsening respiratory symptoms associated with a cold.

What should you not do while using weed?

While using weed, it is important to avoid driving or operating heavy machinery, as cannabis can impair coordination and reaction time. Additionally, excessive use of cannabis without a prescription can lead to negative effects on physical and mental health, including decreased motivation, memory impairment, and increased risk of addiction.


Casey BJ, et al. (2010). The adolescent brain. Ann N Y Acad Sci. doi:10.1111/j.1749-6632.2008.03708.x.

Clark J, et al. (2019). Cannabis and renal function: Considerations in the era of legalization. Curr Opin Nephrol Hypertens. doi:10.1097/MNH.0000000000000521.

Di Forti, M., Quattrone, D., Freeman, T. P., Tripoli, G., Gayer-Anderson, C., Quigley, H., Rodriguez, V., Jongsma, H. E., Ferraro, L., La Cascia, C., La Barbera, D., Tarricone, I., Berardi, D., Szöke, A., Arango, C., Tortelli, A., Velthorst, E., Bernardo, M., Del-Ben, C. M., … van der Ven, E. (2019). The contribution of cannabis use to variation in the incidence of psychotic disorder across Europe (EU-gei): A multicentre case-control study. The Lancet Psychiatry, 6(5), 427–436. https://doi.org/10.1016/s2215-0366(19)30048-3

Diep, C., Tian, C., Vachhani, K., Won, C., Wijeysundera, D. N., Clarke, H., Singh, M., & Ladha, K. S. (2021). Recent cannabis use and nightly sleep duration in adults: A population analysis of the NHANES from 2005 to 2018. Regional Anesthesia & Pain Medicine, 47(2), 100–104. https://doi.org/10.1136/rapm-2021-103161

El Marroun H, et al. (2009). Intrauterine cannabis exposure affects fetal growth trajectories: the Generation R Study. J Am Acad Child Adolesc Psychiatry. doi:10.1097/CHI.0b013e3181adcadf.

Gray KA, et al. (2018). Maternal cannabis use during pregnancy and child neurodevelopmental outcomes. Nat Med. doi:10.1038/s41591-018-0057-5.

Lev-Ran S, et al. (2014). The association between cannabis use and depression: a systematic review and meta-analysis of longitudinal studies. Psychol Med. doi:10.1017/S0033291713001438.

Levine, A., Clemenza, K., Rynn, M., & Lieberman, J. (2017). Evidence for the Risks and Consequences of Adolescent Cannabis Exposure. Journal of the American Academy of Child & Adolescent Psychiatry, 56(3), 214-225. https://doi.org/10.1016/j.jaac.2016.12.014

Lopera, V., Rodríguez, A., & Amariles, P. (2021). Clinical Relevance of Drug Interactions with Cannabis: A Systematic Review. Journal of Clinical Medicine, 11(5), 1154. https://doi.org/10.3390/jcm11051154

Meier MH, et al. (2017). Associations Between Cannabis Use and Physical Health Problems in Early Midlife: A Longitudinal Comparison of Persistent Cannabis vs Tobacco Users. JAMA Psychiatry. doi:10.1001/jamapsychiatry.2017.2893.

Narimatsu S, et al. (2021). Cannabis Use Is Associated With Increased Risk of Acute Liver Injury in Individuals With Common Proxies of Susceptibility to Substance Use Disorder in the United States: A Nationwide Case-Control Study. Clin Gastroenterol Hepatol. doi:10.1016/j.cgh.2020.03.044.

Navarrete, F., Salud, M., Gasparyan, A., Femenía, T., & Manzanares, J. (2020). Cannabis Use in Pregnant and Breastfeeding Women: Behavioral and Neurobiological Consequences. Frontiers in Psychiatry, 11, 586447. https://doi.org/10.3389/fpsyt.2020.586447

Pacheco, D. (2023, October 5). Cannabis for sleep: Benefits and risks. Sleep Foundation. https://www.sleepfoundation.org/sleep-aids/cannabis-and-sleep

Reinders MEJ, et al. (2020). Impact of frequently used drugs on the severity and prognosis of COVID-19. Eur J Pharmacol. doi:10.1016/j.ejphar.2020.173467.

Tetrault JM, et al. (2007). Effects of marijuana smoking on pulmonary function and respiratory complications: a systematic review. Arch Intern Med. doi:10.1001/archinte.167.3.221.

Thomas G, et al. (2020). Medical Marijuana in Cardiovascular Disease: Observational Observations or Observational Misperceptions? J Am Heart Assoc. doi:10.1161/JAHA.119.013653.

Turna J, et al. (2017). Cannabis use behaviors and prevalence of anxiety and depressive symptoms in a cohort of Canadian medicinal cannabis users. J Psychiatr Res. doi:10.1016/j.jpsychires.2017.07.010.

Yankey BN, et al. (2018). Marijuana use and kidney function in U.S. adults. J Am Soc Nephrol. doi:10.1681/ASN.2017101085.

Related Insights

Whilst you’re here you might also like to read…